Info

The project practices Java Selenium 4.0.x release ChromiumDriver to execute the Chrome DevTools Protocol a.k.a. cdp commands - an entirely different set of API communicated to the Chrome browser family via POST requests to /session/$sessionId/goog/cdp/execute with API-specific payload) feature (many of the cdp methods e.g. the DOM ones like

• performSearch,
• getSearchResults
• getNodeForLocation
• getOuterHTML
• querySelectorAll
• querySelector
• getAttributes

overlap with classic Selenium in Classic Javascript and there are few specific ones like:

• addCustomHeaders
• getFrameTree
• setGeolocationOverride
• setDownloadBehavior

to name a few, and various event listeners

This functionality is named in official Selenium Developer Documentation as BiDirectional functionality and BiDi API

The project also exercised other new Selenium 4 API e.g. relative nearby locators whidh did not apear powerful enough yet.

For accessing the Chrome Devtools API with Selenium driver 3.x see cdp_webdriver project

Examples

Async Code Execution by XHR Fetch events in the Browser

This test is opening Wikipedia page and hovers over few links using "classic" Selenium Actions class:

driver.findElement(By.id("mw-content-text")).findElements(By.tagName("a")).stream().forEach( (WebElement element ) -> {
    new Actions(driver).moveToElement(element).build().perform();
  }
}

To emphacise that the lambda operates "classic" object,the WebElement type was entered explicitly.

In the @Before -annotated method in the test class, the Fetch API is enabled for all requests

@Before
public void beforeTest() throws Exception {
chromeDevTools = ((HasDevTools) driver).getDevTools();

List<RequestPattern> reqPattern = new ArrayList<>();
reqPattern.add(new RequestPattern(Optional.of("*"), Optional.of(ResourceType.XHR), Optional.of(RequestStage.RESPONSE)));
chromeDevTools.send(Fetch.enable(Optional.of(reqPattern), Optional.of(false)));

(If necessary one can limit to subset of reuests via match pattern). Then in the test method callback is set up:

@Test
public void test() {
	chromeDevTools.addListener(Fetch.requestPaused(),
		(RequestPaused event) -> {
      event.getResponseHeaders().get().stream().map((HeaderEntry entry) -> String.format("%s: %s",
              entry.getName(), entry.getValue())).collect(Collectors.toList());
      Fetch.GetResponseBodyResponse response = chromeDevTools.send(Fetch.getResponseBody(event.getRequestId()));
        String body = new String(Base64.decodeBase64(response.getBody().getBytes("UTF8")));
	System.err.println("response body:\n" + body);
      }
});
// he mouse hover actions to follow

This allows capture every Ajax request response headers,

List<HeaderEntry> headerEntries = event.getResponseHeaders().isPresent() ? event.getResponseHeaders().get() : new ArrayList<>();
List<String> headers = headerEntries.stream().map(entry -> String.format("%s: %s", entry.getName(), entry.getValue())) .collect(Collectors.toList());

along with response status

event.getResponseStatusCode().get()

and body which is usually a base64 encoded JSON with multiple details, processed by browser

Fetch.GetResponseBodyResponse response = chromeDevTools.send(Fetch.getResponseBody(event.getRequestId()));
String body = null;
if (response.getBase64Encoded()) {
	try {
		body = new String( Base64.decodeBase64(response.getBody().getBytes("UTF8")));
	} catch (UnsupportedEncodingException e) {
		System.err.println("Exception (ignored): " + e.toString());
	}
} else {
	body = response.getBody();
}

finally the test continues default processing of the request:

chromeDevTools.send(Fetch.continueRequest(
	event.getRequestId(),
	Optional.empty(),
	Optional.empty(),
	Optional.empty(),
	Optional.empty(),
	Optional.empty()));

• the arguments to the Java adapter method match the Javascript Fetch.continueResponse parameter definition:

requestId
RequestId
An id the client received in requestPaused event.
responseCode
integer
An HTTP response code. If absent, original response code will be used.
responsePhrase
string
A textual representation of responseCode. If absent, a standard phrase matching responseCode is used.
responseHeaders
array[ HeaderEntry ]
Response headers. If absent, original response headers will be used.
binaryResponseHeaders
string
Alternative way of specifying response headers as a \0-separated series of name: value pairs. Prefer the above method unless you need to represent some non-UTF8 values that can't be transmitted over the protocol as text. (Encoded as a base64 string when passed over JSON)

Access Browser Console Logs

Browser console logs may accessed asynchronuosly in asimilar fashion:

@Before
public void beforeTest() throws Exception {
	chromeDevTools.send(Log.enable());
	chromeDevTools.addListener(Log.entryAdded(),
		(LogEntry event) -> System.err.println(
			String.format( "time stamp: %s line number: %s url: \"%s\" text: %s",
	formatTimestamp(event.getTimestamp()),
	(event.getLineNumber().isPresent() ? event.getLineNumber().get() : ""),
	(event.getUrl().isPresent() ? event.getUrl().get() : ""),
	event.getText())));
}

The properties of the event are taken from Log entry object specification One can also confirm the logging event to have expected properties, e.g. message:

@Test
public void test() {
	final String consoleMessage = "Lorem ipsum";
	chromeDevTools.addListener(Log.entryAdded(),
		(LogEntry event) -> assertThat(event.getText(), containsString(consoleMessage)));
	if (driver instanceof JavascriptExecutor) {
		JavascriptExecutor executor = JavascriptExecutor.class.cast(driver);		
		executor.executeScript("console.log(arguments[0]);", consoleMessage);
	}
}

Print to PDF

This API uses CDP command:

public void test1() {
	PrintToPDFResponse response;
	boolean landscape = false;
	boolean displayHeaderFooter = false;
	boolean printBackground = false;
	Page.PrintToPDFTransferMode transferMode = Page.PrintToPDFTransferMode.RETURNASBASE64;
	int scale = 1;

	// Act
	response = chromeDevTools.send(Page.printToPDF(
	Optional.of(landscape),
	Optional.of(displayHeaderFooter),
	Optional.of(printBackground),
	Optional.of(scale),
	Optional.empty(),
	Optional.empty(),
	Optional.empty(),
	Optional.empty(),
	Optional.empty(),
	Optional.empty(),
	Optional.empty(),
	Optional.empty(),
	Optional.empty(),
	Optional.empty(),
	Optional.empty(),
	Optional.of(transferMode)));
	assertThat(response, notNullValue());
	String body = new String(Base64.decodeBase64(response.getData().getBytes("UTF8")));
	assertThat(body, notNullValue());
	String magic = body.substring(0, 9);
	assertThat(magic, containsString("%PDF"));

the browser needs to run headless mode for the call to succeed the alternative call signature is

response = chromeDevTools.send(new Command<PrintToPDFResponse>("Page.printToPDF", ImmutableMap.of("landscape", landscape), o -> o.read(PrintToPDFResponse.class)));
assertThat(response, notNullValue());

for some calls (but not specifically for Page.printToPDF) yet anoher alternavie signature via static method exists

response = chromeDevTools.send(new Command<PrintToPDFResponse>("Page.printToPDF", ImmutableMap.of("landscape", landscape), ConverterFunctions.map("data", PrintToPDFResponse.class)));

Zoom the Browser window

in additon to legacy-like keyboard zoom, the CDP supports Page.setDeviceMetricsOverride method and Emulation.setDeviceMetricsOverride method:

  @Before
  public void before() throws Exception {
    baseURL = "https://www.wikipedia.org";
    driver.get(baseURL);
  }

  @Test
  public void test1() {
    for (int cnt = 0; cnt != deviceScaleFactors.length; cnt++) {
      double deviceScaleFactor = deviceScaleFactors[cnt];
      screenshotFileName = String.format("test1_%03d.jpg",
          (int) (100 * deviceScaleFactor));
      layoutMetrics = chromeDevTools.send(Page.getLayoutMetrics());
      rect = layoutMetrics.getContentSize();
      width = rect.getWidth().intValue();
      height = rect.getHeight().intValue();
      System.err.println(String.format("Content size: %dx%d", width, height));
      chromeDevTools.send(
        // @formatter:off
        Emulation.setDeviceMetricsOverride(
          rect.getWidth().intValue(),
          rect.getHeight().intValue(),
          deviceScaleFactor,
          false,
          Optional.empty(),
          Optional.empty(),
          Optional.empty(),
          Optional.empty(),
          Optional.empty(),
          Optional.empty(),
          Optional.empty(),
          Optional.empty(),
          Optional.empty()
        )
        // @formatter:on
      );
      String dataString = chromeDevTools.send(
        // @formatter:off
        Page.captureScreenshot(
            Optional.of(Page.CaptureScreenshotFormat.JPEG),
            Optional.of(100),
            Optional.empty(),
            Optional.of(true),
            Optional.of(true)
        )
        // @formatter:off
    );
    chromeDevTools.send(Emulation.clearDeviceMetricsOverride());

    byte[] image = base64.decode(dataString);
    try {
      BufferedImage o = ImageIO.read(new ByteArrayInputStream(image));
      System.err.println(String.format("Screenshot dimensions: %dx%d",
          o.getWidth(), o.getHeight()));
      assertThat((int) (width * deviceScaleFactor) - o.getWidth(),
          not(greaterThan(2)));
      assertThat((int) (height * deviceScaleFactor) - o.getHeight(),
          not(greaterThan(2)));
    } catch (IOException e) {
      System.err.println("Exception loading image (ignored): " + e.toString());
    }
    try {
      FileOutputStream fileOutputStream = new FileOutputStream(
          screenshotFileName);
      fileOutputStream.write(image);
      fileOutputStream.close();
    } catch (IOException e) {
      System.err.println("Exception saving image (ignored): " + e.toString());
    }
    }
  }


@After
public void clearPage() {
  chromeDevTools.send(CSS.disable());
  try {
    chromeDevTools.send(DOM.disable());
  } catch (DevToolsException e) {
    // DOM agent hasn't been enabled
  }
  driver.get("about:blank");
}

this test gets gradually magnified out page screen shots:

alternatively use CDP commands for the same:

  @SuppressWarnings("unchecked")
  @Test
  public void test() {
    // Assert
    params = new HashMap<>();
    for (int cnt = 0; cnt != deviceScaleFactors.length; cnt++) {
      double deviceScaleFactor = deviceScaleFactors[cnt];
      filename = String.format("test2_%03d.jpg",
          (int) (100 * deviceScaleFactor));

      try {
        command = "Page.getLayoutMetrics";
        result = driver.executeCdpCommand(command, new HashMap<>());
        System.err
            .println("Page.getLayoutMetrics: " + result.get("contentSize"));
        rect = (Map<String, Long>) result.get("contentSize");
        height = rect.get("height");
        width = rect.get("width");
        command = "Emulation.setDeviceMetricsOverride";
        // Act
        System.err.println(String.format("Scaling to %02d%% %s",
            (int) (100 * deviceScaleFactor), filename));
        params.clear();
        params.put("deviceScaleFactor", deviceScaleFactor);
        params.put("width", width);
        params.put("height", height);
        params.put("mobile", false);
        params.put("scale", 1);
        driver.executeCdpCommand(command, params);

        Utils.sleep(delay);
        command = "Page.captureScreenshot";
        // Act
        result = driver.executeCdpCommand(command,
            new HashMap<String, Object>());

        command = "Emulation.clearDeviceMetricsOverride";
        driver.executeCdpCommand(command, new HashMap<String, Object>());

        // Assert
        assertThat(result, notNullValue());
        assertThat(result, hasKey("data"));
        dataString = (String) result.get("data");
        assertThat(dataString, notNullValue());

        byte[] image = base64.decode(dataString);
        BufferedImage o = ImageIO.read(new ByteArrayInputStream(image));
        assertThat(o.getWidth(), greaterThan(0));
        assertThat(o.getHeight(), greaterThan(0));
        FileOutputStream fileOutputStream = new FileOutputStream(filename);
        fileOutputStream.write(image);
        fileOutputStream.close();
      } catch (IOException e) {
        System.err.println("Exception saving image (ignored): " + e.toString());
      } catch (JsonSyntaxException e) {
        System.err.println("JSON Syntax exception in " + command
            + " (ignored): " + e.toString());
      } catch (WebDriverException e) {
        // willbe thrown if the required arguments are not provided.
        // TODO: add failing test
        System.err.println(
            "Web Driver exception in " + command + " (ignored): " + Utils
                .processExceptionMessage(e.getMessage() + "  " + e.toString()));
      } catch (Exception e) {
        System.err.println("Exception in " + command + "  " + e.toString());
        throw (new RuntimeException(e));
      }
    }
  }

Filter URL

Bandwidth improving filtering of certain mask URLs

chromeDevTools.send(Network.enable(Optional.of(100000000), Optional.empty(), Optional.empty()));
chromeDevTools.send(Network.setBlockedURLs(ImmutableList.of("*.css", "*.png", "*.jpg", "*.gif", "*favicon.ico")));
driver.get("http://arngren.net");

one can also log the *.css, *.jpg *.png and *.ico blocking in action:

// verify that
chromeDevTools.addListener(Network.loadingFailed(),
	(LoadingFailed event) -> {
		ResourceType resourceType = event.getType();
		if (resourceType.equals(ResourceType.STYLESHEET)
				|| resourceType.equals(ResourceType.IMAGE)
				|| resourceType.equals(ResourceType.OTHER)) {
			Optional<BlockedReason> blockedReason = event.getBlockedReason();
			assertThat(blockedReason.isPresent(), is(true));
			assertThat(blockedReason.get(), is(BlockedReason.INSPECTOR));
		}
	System.err.println("Blocked event: " + event.getType());
});

finally one can disable filtering:

// set request interception only for css requests
RequestPattern requestPattern = new RequestPattern(Optional.of("*.gif"), Optional.of(ResourceType.IMAGE), Optional.of(InterceptionStage.HEADERSRECEIVED));
chromeDevTools.send(Network.setRequestInterception(ImmutableList.of(requestPattern)));
chromeDevTools.send(Page.navigate(baseURL, Optional.empty(),Optional.empty(), Optional.empty(), Optional.empty()));

Override User Agent

One can call cdp protocol to invoke setUserAgentOverride method and dynmically modify the user-agent header during the test:

  import org.openqa.selenium.chrome.ChromeDriver;
  import org.openqa.selenium.chromium.ChromiumDriver;

  ChromiumDriver driver = new ChromeDriver();
  driver.get("https://www.whoishostingthis.com/tools/user-agent/");
  By locator = By.cssSelector(".user-agent");
  WebElement element = driver.findElement(locato);
  assertThat(element.getAttribute("innerText"), containsString("Mozilla"));
  Map<String, Object> params = new HashMap<String, Object>();
  params.put("userAgent", "python 2.7");
  params.put("platform", "Windows");
  driver.executeCdpCommand("Network.setUserAgentOverride", params);
  driver.navigate().refresh();
  sleep(100);

  element = driver.findElement(locator);
  assertThat(element.isDisplayed(), is(true));
  assertThat(element.getAttribute("innerText"), is("python 2.7"));

demonstrates that the user-agent is indeed changing

Cookies

The example shows alternative API to collect the cookies available to page Javascript

  Map<String, Object> result = driver.executeCdpCommand("Page.getCookies", new HashMap<String, Object>());
  ArrayList<Map<String, Object>> cookies = (ArrayList<Map<String, Object>>) result.get("cookies");
  cookies.stream().limit(100).map(o -> o.keySet()).forEach(System.err::println);

Capture Screenshot

  String result = driver.executeCdpCommand("Page.captureScreenshot", new HashMap<>());
  String data = (String) result.get("data");
  byte[] image = new (Base64()).decode(data);
  assertThat(ImageIO.read(new ByteArrayInputStream(image)).getWidth(), greaterThan(0));
  (new FileOutputStream("temp.png")).write(image);

Capture Element Screenshot

implements the clipping to viewport functioality

command = "Page.captureScreenshot";
params = new HashMap<String, Object>();
Map<String, Object> viewport = new HashMap<>();
System.err.println("Specified viewport: " + String
    .format("x=%d, y=%d, width=%d, height=%d", x, y, width, height));
viewport.put("x", (double) x);
viewport.put("y", (double) y);
viewport.put("width", (double) width);
viewport.put("height", (double) height);
viewport.put("scale", scale);
params.put("clip", viewport);
result = driver.executeCdpCommand(command, params);
dataString = (String) result.get("data");
assertThat(dataString, notNullValue());
Base64 base64 = new Base64();
byte[] image = base64.decode(dataString);
String screenshotFileName = String.format("card%02d.png", cnt);
FileOutputStream fileOutputStream = new FileOutputStream( screenshotFileName);
fileOutputStream.write(image);
fileOutputStream.close();

Note: some CDP API notably Page.printToPDF are not curently implemented:

unhandled inspector error: {"code":-32000,"message":"PrintToPDF is not implemented"}(..)

Custom Headers

This can be done both at the wrapper methods

    // enable Network
    chromeDevTools.send(Network.enable(Optional.empty(), Optional.empty(), Optional.empty()));
    headers = new HashMap<>();
    headers.put("customHeaderName", "customHeaderValue");
    Headers headersData = new Headers(headers);
    chromeDevTools.send(Network.setExtraHTTPHeaders(headersData));

The validation can be done through hooking assert and log message to the event:

    // add event listener to log that requests are sending with the custom header
    chromeDevTools.addListener(Network.requestWillBeSent(),
        o -> Assert.assertEquals(o.getRequest().getHeaders().get("customHeaderName"), "customHeaderValue"));
    chromeDevTools.addListener(Network.requestWillBeSent(), o -> System.err.println(
        "addCustomHeaders Listener invoked with " + o.getRequest().getHeaders().get("customHeaderName")));

and low level "commands":

    String command = "Network.enable";
    params = new HashMap<>();
    params.put("maxTotalBufferSize", 0);
    params.put("maxPostDataSize", 0);
    params.put("maxPostDataSize", 0);
    result = driver.executeCdpCommand(command, params);
    command = "Network.setExtraHTTPHeaders";

    params = new HashMap<>();
    Map<String, String> headers = new HashMap<>();
    headers.put("customHeaderName", this.getClass().getName() + " addCustomHeadersTest");
    params.put("headers", headers);
    result = driver.executeCdpCommand(command, params);

To test one can e.g. fire a tomcat server with request header logging and send the GET request

driver.get("http://127.0.0.1:8080/demo/Demo");

The actual validation will be done through console logs inspection of the server

DOM Node Navigation

The following somewhat long test exercises steps one has to perform with CDP to get a specific DOM Node focused and act upon:

It appears every node search starts with getting the document:

	@SuppressWarnings("unchecked")
	@Test
	public void getDocumentTest() {
		// Arrange
		driver.get("https://www.google.com");
		String command = "DOM.getDocument";
		try {
			// Act
			result = driver.executeCdpCommand(command, new HashMap<>());
			// Assert
			assertThat(result, hasKey("root"));
			Map<String, Object> data =  (Map<String, Object>) result.get("root");
			assertThat(data, hasKey("nodeId"));
			assertTrue(Long.parseLong(data.get("nodeId").toString()) != 0);
			err.println("Command " + command + " return node: "
					+ new Gson().toJson(data, Map.class));
		} catch (org.openqa.selenium.WebDriverException e) {
			err.println(
					"Exception in command " + command + " (ignored): " + e.toString());
		}
	}

This test logs:

Command DOM.getDocument return node:
{
  "backendNodeId": 1,
  "baseURL": "https://www.google.com/",
  "childNodeCount": 2,
  "children": [
    {
      "backendNodeId": 2,
      "localName": "",
      "nodeId": 10,
      "nodeName": "html",
      "nodeType": 10,
      "nodeValue": "",
      "parentId": 9,
      "publicId": "",
      "systemId": ""
    },
    {
      "attributes": [
        "itemscope",
        "",
        "itemtype",
        "http://schema.org/WebPage",
        "lang",
        "en"
      ],
      "backendNodeId": 3,
      "childNodeCount": 2,
      "children": [
        {
          "attributes": [],
          "backendNodeId": 21,
          "childNodeCount": 12,
          "localName": "head",
          "nodeId": 12,
          "nodeName": "HEAD",
          "nodeType": 1,
          "nodeValue": "",
          "parentId": 11
        },
        {
          "attributes": [
            "jsmodel",
            " ",
            "class",
            "hp vasq",
            "id",
            "gsr"
          ],
          "backendNodeId": 22,
          "childNodeCount": 8,
          "localName": "body",
          "nodeId": 13,
          "nodeName": "BODY",
          "nodeType": 1,
          "nodeValue": "",
          "parentId": 11
        }
      ],
      "frameId": "C3CE739B971DD10AFECA84F6C1554308",
      "localName": "html",
      "nodeId": 11,
      "nodeName": "HTML",
      "nodeType": 1,
      "nodeValue": "",
      "parentId": 9
    }
  ],
  "documentURL": "https://www.google.com/",
  "localName": "",
  "nodeId": 9,
  "nodeName": "#document",
  "nodeType": 9,
  "nodeValue": "",
  "xmlVersion": ""
}

now one can

		command = "DOM.querySelector";
		params.clear();
		params.put("nodeId", nodeId);
		params.put("selector", "img#hplogo");

		try {
			result = driver.executeCdpCommand(command, params);
			assertThat(result, hasKey("nodeId"));
			nodeId = (Long) result.get("nodeId");
			assertTrue(nodeId != 0);
			err.println("Command " + command + " returned  nodeId: " + nodeId);
		} catch (org.openqa.selenium.WebDriverException e) {
			err.println(
					"Exception in command " + command + " (ignored): " + e.toString());
		}
		command = "DOM.getOuterHTML";
		params.clear();
		params.put("nodeId", nodeId);
		
		try {
			result = driver.executeCdpCommand(command, params);
			assertThat(result, notNullValue());
			assertThat(result, hasKey("outerHTML"));
			String dataString = (String) result.get("outerHTML");
			assertThat(dataString, notNullValue());
			err.println("Command " + command + " return outerHTML: " + dataString);
		} catch (Exception e) {
			err.println("Exception in " + command + " (ignored): " + e.toString());
		}
	}

This will log:

Command DOM.querySelector returned  nodeId: 162

Command DOM.getOuterHTML return outerHTML:
<img alt="Google" height="92" id="hplogo"  src="/images/branding/googlelogo/2x/googlelogo_color_272x92dp.png"  style="padding-top:109px" width="272" onload="typeof google==='object'&amp;&amp;google.aft&amp;&amp;google.aft(this)" data-iml="1576602836994" data-atf="1">

collapsing multiple command calls together will lead to somewhat bloated test method

	@Test
	public void multiCommandTest() {
		// Arrange
		baseURL = "https://www.google.com";
		driver.get(baseURL);
		String command = "DOM.getDocument";
		try {
			// Act
			result = driver.executeCdpCommand(command, new HashMap<>());
			// Assert
			assertThat(result, hasKey("root"));
			@SuppressWarnings("unchecked")
			Map<String, Object> node = (Map<String, Object>) result.get("root");
			assertThat(node, hasKey("nodeId"));
			nodeId = Long.parseLong(node.get("nodeId").toString());
			assertTrue(nodeId != 0);
			err.println("Command " + command + " returned nodeId: " + nodeId);
		} catch (org.openqa.selenium.WebDriverException e) {
			err.println(
					"Exception in command " + command + " (ignored): " + e.toString());
		}
		command = "DOM.describeNode";
		params = new HashMap<>();
		params.put("nodeId", nodeId);
		params.put("depth", 1);
		try {
			result = driver.executeCdpCommand(command, params);
			// Assert
			assertThat(result, hasKey("node"));
			@SuppressWarnings("unchecked")
			Map<String, Object> data = (Map<String, Object>) result.get("node");
			for (String field : Arrays.asList(
					new String[] { "nodeType", "nodeName", "localName", "nodeValue" })) {
				assertThat(data, hasKey(field));
			}
			System.err.println("Command " + command + " returned node: " + data);
		} catch (org.openqa.selenium.WebDriverException e) {
			err.println(
					"Exception in command " + command + " (ignored): " + e.toString());
		}

		command = "DOM.querySelector";
		params = new HashMap<>();
		params.put("nodeId", nodeId);
		// params.put("selector", "img#hplogo");
		params.put("selector", "input[name='q']");

		try {
			result = driver.executeCdpCommand(command, params);
			// depth, 1
			// Assert
			assertThat(result, hasKey("nodeId"));
			// @SuppressWarnings("unchecked")
			nodeId = Long.parseLong(result.get("nodeId").toString());
			assertTrue(nodeId != 0);
			err.println("Command " + command + " returned  nodeId: " + nodeId);
		} catch (org.openqa.selenium.WebDriverException e) {
			err.println(
					"Exception in command " + command + " (ignored): " + e.toString());
		}

		command = "DOM.resolveNode";
		params = new HashMap<>();
		params.put("nodeId", nodeId);

		try {
			result = driver.executeCdpCommand(command, params);
			// depth, 1
			// Assert
			assertThat(result, hasKey("object"));
			// object
			@SuppressWarnings("unchecked")
			Map<String, Object> data = (Map<String, Object>) result.get("object");
			for (String field : Arrays.asList(
					new String[] { "type", "subtype", "className", "objectId" })) {
				assertThat(data, hasKey(field));
			}
			String objectId = (String) data.get("objectId");
			assertThat(objectId, notNullValue());
			System.err
					.println("Command " + command + " returned objectId: " + objectId);
		} catch (org.openqa.selenium.WebDriverException e) {
			err.println(
					"Exception in command " + command + " (ignored): " + e.toString());
		}

		command = "DOM.something not defined";
		try {
			// Act
			result = driver.executeCdpCommand(command, new HashMap<>());
		} catch (org.openqa.selenium.WebDriverException e) {
			err.println(
					"Exception in command " + command + " (ignored): " + e.toString());
			// wasn't found
		}
		// DOM.removeNode
		command = "DOM.focus";
		params = new HashMap<>();
		params.put("nodeId", nodeId);
		try {
			// Act
			result = driver.executeCdpCommand(command, params);
		} catch (org.openqa.selenium.WebDriverException e) {
			err.println(
					"Exception in command " + command + " (ignored): " + e.toString());
			// : unknown error: unhandled inspector error:
			// {"code":-32000,"message":"Element is not focusable"}
		}
		command = "DOM.highlightNode";
		try {
			// Act
			result = driver.executeCdpCommand(command, new HashMap<>());
			Utils.sleep(10000);
		} catch (org.openqa.selenium.WebDriverException e) {
			err.println(
					"Exception in command " + command + " (ignored): " + e.toString());
		}
		// TODO: command = "Runtime.callFunctionOn";
	}

Relative Locators

Selenum release dependency

The selenium-chromium-driver that is only available for Selenum release 4 is the critical dependency jar of this project. The selenium-chromium-driver repository search page.

The devtools and chromium subprojects of selenium client of official seleniumhq/selenium project have no dependencies and can be cloned and built locally allowing one to use CDP API with Selenium 3.x e.g. Selenium 3.13.0. This is currently attempted this way in this project. Moving away form default 4.0.0.alpha maven profiles is a work in progress.

Breaking Changes in Selenium 4.0.0-alpha-7

With Selenium driver release 4.0.0-alpha-7 just to make the project compile changes imported package names need to change all org.openqa.selenium.devtools.browser references with org.openqa.selenium.devtools.v87.browser and similar to other packages inside org.openqa.selenium.devtools were requied. Without this multiple compile errors like:

package org.openqa.selenium.devtools.browser does not exist

are observed

Also the following run time errors indicate that selenium-api-4.0.0-alpha-7.jar was build on JDK 11 and is notloadable in JDK 8.

This manifests through the runtime exception

java.lang.NoClassDefFoundError: Could not initialize class org.openqa.selenium.net.PortProber
  at org.openqa.selenium.remote.service.DriverService$Builder.build(DriverService.java:401)
  at org.openqa.selenium.chrome.ChromeDriverService.createServiceWithConfig(ChromeDriverService.java:133)

the usual classpath scan reveals the jar containing the class in question, to be actually present in classpath

find ~/.m2/repository/ -iname 'selenium*jar' |xargs -IX sh -c "echo X; jar tvf X" | tee a

and method signature exception

java.lang.NoSuchMethodError: java.io.FileReader.<init>(Ljava/io/File;Ljava/nio/charset/Charset;)V
  at org.openqa.selenium.net.LinuxEphemeralPortRangeDetector.getInstance(LinuxEphemeralPortRangeDetector.java:36)
  at org.openqa.selenium.net.PortProber.<clinit>(PortProber.java:42)

the method the exception is complainign was added in Java 11

Note

• To get Google Chrome updates past version 108, one needs Windows 10 or later. Some development environment computers are using Windows 8.1

Note

• When Chromium browser installed via snapd on Ubuntu 20.04, all tests are failing with

org.openqa.selenium.SessionNotCreatedException: Could not start a new session. Response code 500. Message: unknown error: DevToolsActivePort file doesn't exist
Host info: host: 'lenovoy40-1', ip: '127.0.1.1'
Build info: version: '4.10.0', revision: 'c14d967899'
System info: os.name: 'Linux', os.arch: 'amd64', os.version: '5.4.0-150-generic', java.version: '1.8.0_161'
Driver info: org.openqa.selenium.chrome.ChromeDriver
Command: [null, newSession {capabilities=[Capabilities {browserName: chrome, goog:chromeOptions: {args: [--remote-allow-origins=*, --allow-insecure-localhost, --allow-running-insecure-co..., --browser.download.folderLi..., --browser.helperApps.neverA..., --disable-blink-features=Au..., --disable-default-app, --disable-dev-shm-usage, --disable-extensions, --disable-gpu, --disable-infobars, --disable-in-process-stack-..., --disable-logging, --disable-notifications, --disable-popup-blocking, --disable-save-password-bubble, --disable-translate, --disable-web-security, --enable-local-file-accesses, --ignore-certificate-errors, --ignore-certificate-errors, --ignore-ssl-errors=true, --log-level=3, --no-proxy-server, --no-sandbox, --output=/dev/null, --ssl-protocol=any, --user-agent=Mozilla/5.0 (W...], extensions: []}}]}]
	at org.openqa.selenium.remote.ProtocolHandshake.createSession(ProtocolHandshake.java:140)
	at org.openqa.selenium.remote.ProtocolHandshake.createSession(ProtocolHandshake.java:96)
	at org.openqa.selenium.remote.ProtocolHandshake.createSession(ProtocolHandshake.java:68)
	at org.openqa.selenium.remote.HttpCommandExecutor.execute(HttpCommandExecutor.java:163)
	at org.openqa.selenium.remote.service.DriverCommandExecutor.invokeExecute(DriverCommandExecutor.java:196)
	at org.openqa.selenium.remote.service.DriverCommandExecutor.execute(DriverCommandExecutor.java:171)
	at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:531)
	at org.openqa.selenium.remote.RemoteWebDriver.startSession(RemoteWebDriver.java:227)
	at org.openqa.selenium.remote.RemoteWebDriver.<init>(RemoteWebDriver.java:154)
	at org.openqa.selenium.chromium.ChromiumDriver.<init>(ChromiumDriver.java:107)
	at org.openqa.selenium.chrome.ChromeDriver.<init>(ChromeDriver.java:87)
	at org.openqa.selenium.chrome.ChromeDriver.<init>(ChromeDriver.java:82)
	at org.openqa.selenium.chrome.ChromeDriver.<init>(ChromeDriver.java:71)
	at com.github.sergueik.selenium.BaseCdpTest.beforeClass(BaseCdpTest.java:124)

• when Chromium browser installed via apt, from

sudo add-apt-repository ppa:system76/pop
sudo apt update
sudo apt install -y -q chromium

the tests would work but the browser is quite old version 83.

The latest available version of chromium-broser on http://archive.ubuntu.com/ubuntu/pool/universe/c/chromium-browser/ is 112

NOTE: will have to download a few packages to be able to install chromium-browser:

• chromium-browser_112.0.5615.49-0ubuntu0.18.04.1_amd64.deb
• chromium-browser-l10n_112.0.5615.49-0ubuntu0.18.04.1_all.deb
• chromium-codecs-ffmpeg_112.0.5615.49-0ubuntu0.18.04.1_amd64.deb
• chromium-codecs-ffmpeg-extra_112.0.5615.49-0ubuntu0.18.04.1_amd64.deb

and install them in specific order:

dpkg -i chromium-codecs-ffmpeg_112.0.5615.49-0ubuntu0.18.04.1_amd64.deb
dpkg -i chromium-codecs-ffmpeg-extra_112.0.5615.49-0ubuntu0.18.04.1_amd64.deb
dpkg -i chromium-browser_112.0.5615.49-0ubuntu0.18.04.1_amd64.deb

Since the version mismatch the test log will contain plenty of

Match
WARNING: Unable to find CDP implementation matching 112
Jun 15, 2023 9:56:53 AM org.openqa.selenium.chromium.ChromiumDriver lambda$new$4
WARNING: Unable to find version of CDP to use for . You may need to include a dependency on a specific version of the CDP using something similar to `org.seleniumhq.selenium:selenium-devtools-v86:4.10.0` where the version ("v86") matches the version of the chromium-based browser you're using and the version number of the artifact is the same as Selenium's.

• when Chrome latest stable deb package is downloaded and chrome is installed via dpkg

cd ~/Downloads
wget https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb
sudo apt install -y -q ./google-chrome-stable_current_amd64.deb

a longer version

cd ~/Downloads
wget -nv "https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb"
sudo apt-get install -qqy libxss1 libappindicator1 libindicator7
sudo dpkg -i google-chrome-stable_current_amd64.deb
rm google-chrome-stable_current_amd64.deb
sudo apt-get install -qqy -f google-chrome-stable

dpkg -l google-chrome-stable

Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name           Version      Architecture Description
+++-==============-============-============-=================================
ii  google-chrome- 114.0.5735.1 amd64        The web browser from Google

Download latest Chromedriver

CHROMEDRIVER_VERSION=$(curl -s "http://chromedriver.storage.googleapis.com/LATEST_RELEASE")
PACKAGE_ARCHIVE='chromedriver_linux64.zip'
PLATFORM=linux64
URL="http://chromedriver.storage.googleapis.com/${CHROMEDRIVER_VERSION}/chromedriver_${PLATFORM}.zip"
wget -O $PACKAGE_ARCHIVE -nv $URL
unzip -o $PACKAGE_ARCHIVE

NOTE: the latest version of Chrome Driver that can be downloaded this way is 114.0.5735.90

the tests work

NOTE: is is better to use

dpkg -i ./google-chrome-stable_current_amd64.deb

the apt has the warning:

W: Repository is broken: google-chrome-stable:amd64 (= 114.0.5735.133-1) has no Size information

File Download Browser Behavior

one may configure `` and subscribe to events Browser.downloadWillBegin and `Browser.downloadProgress` via CDP:

chromeDevTools.addListener(Browser.downloadWillBegin(),
	(DownloadWillBegin o) -> {
		System.err.println("in Browser.downloadWillBegin listener. url: " + o.getUrl() + "\tfilename: " + o.getSuggestedFilename());
});
List<DownloadProgress.State> states = new ArrayList<>();
chromeDevTools.addListener(Browser.downloadProgress(),
	(DownloadProgress o) -> {
		DownloadProgress.State state = o.getState();
		System.err.println("in Browser.downloadProgress listener. state: " + state.toString());
		states.add(state);
});

in Browser.downloadWillBegin listener. url: https://scholar.harvard.edu/files/torman_personal/files/samplepptx.pptx     filename: samplepptx.pptx
in Browser.downloadProgress listener. state: inProgress
in Browser.downloadProgress listener. state: inProgress
in Browser.downloadProgress listener. state: inProgress
in Browser.downloadProgress listener. state: inProgress
in Browser.downloadProgress listener. state: inProgress
in Browser.downloadProgress listener. state: inProgress
in Browser.downloadProgress listener. state: inProgress
in Browser.downloadProgress listener. state: inProgress
in Browser.downloadProgress listener. state: inProgress
in Browser.downloadProgress listener. state: inProgress
in Browser.downloadProgress listener. state: completed
in Browser.downloadProgress listener. state: completed
Inspecting downloaded filename: f5a83cbd-97fb-451e-8651-618f63c1ec59
Verified downloaded file: f5a83cbd-97fb-451e-8651-618f63c1ec59 in /tmp

Note

Starting with version 115 the Chrome browser and ChromeDriver information is located on Chrome for Testing availability dashboard page. A broader listing of Chrome versions can be found in https://googlechromelabs.github.io/chrome-for-testing/known-good-versions-with-downloads.json:

curl -k -O https://googlechromelabs.github.io/chrome-for-testing/known-good-versions-with-downloads.json

jq '.versions[] | select(.version | contains( "114.")) ' known-good-versions-with-downloads.json  | jq '.downloads[]|.[]|select(.platform |contains("linux64"))'

{
  "platform": "linux64",
  "url": "https://edgedl.me.gvt1.com/edgedl/chrome/chrome-for-testing/114.0.5696.0/linux64/chrome-linux64.zip"
}

• extract the chrome and chromedriver links via jq (unfinished for chromedriver, save the full JSON locally and finish the query)

The instructions of version lookup are provided on version selection hint page. Prior to that the chromedriver download links were posted on Chromedriver Downloads page

• With Selenium version 4.14.0 onwards one has to build it on JDK 11_ or later, even if targeting Java 1.8 in pom.xml - * Require Java 11 (#12843) is noted in the Selenium Changelog.

The attempt to build with JDK 1.8 fails with

[ERROR] bad class file: .m2\repository\org\seleniumhq\selenium\selenium-api\4.14.0\selenium-api-4.14.0.jar
[ERROR] class file has wrong version 55.0, should be 52.0

Note

if seeing the version mismatch error in every test:

mvn test

org.openqa.selenium.SessionNotCreatedException: Could not start a new session. Response code 500. Message: session not created: This version of ChromeDriver only supports Chrome version 122
Current browser version is 121.0.6167.85 with binary path /opt/google/chrome/chrome

make sure to have the google repository added:

echo "deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main" | sudo tee /etc/apt/sources.list.d/google-chrome.list

and the error is cleared:

apt-get install google-chrome-stable
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package google-chrome-stable is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'google-chrome-stable' has no installation candidate

dpkg-reconfigure google-chrome-stable
/usr/sbin/dpkg-reconfigure: google-chrome-stable is broken or not fully installed

the install the chrome:

apt-get install google-chrome-stable

and confirm the test to pass

Debugging File Upload

A textbook File Upload Form looks like below

<html>
<head>
<title>File Upload Test</title>
</head>

<body>
<h1>File Upload Test</h1>
<form enctype = "multipart/form-data" action="upload endpoint url" method="POST">
upload file path: <input name="upload file path" type="file">
<input type="submit" value="send file">
</form>
</body>

The requirements for plain browser-driven file upload HTML page are:

• form must specify the POST method
• form must specify an enctype of multipart/form-data
• form must contain an <input type="file"> element

To examine the upload request genetated by the browser, subscribe to `` event:

Map<String, Map<String, Object>> requests = new HashMap<>();
chromeDevTools.send(Network.enable(Optional.empty(), Optional.empty(), Optional.empty()));
chromeDevTools.addListener(Network.requestWillBeSent(),
  (RequestWillBeSent event) ->
    requests.put(event.getRequest().getUrl(), event.getRequest().getHeaders().toJson())
);

and perform the upload:

wait = new WebDriverWait(driver, Duration.ofSeconds(flexibleWait));
wait.pollingEvery(Duration.ofMillis(pollingInterval));
actions = new Actions(driver);
url = "https://ps.uci.edu/~franklin/doc/file_upload.html";
driver.get(url);
element = wait.until(ExpectedConditions.visibilityOfElementLocated(By.cssSelector("input[name='userfile']")));

assertThat(element.isDisplayed(), is(true));
Utils.highlight(element);
element.sendKeys(dummy.getAbsolutePath());

element = driver.findElement(By.tagName("form"));
assertThat(element, notNullValue());
assertThat(element.getAttribute("action"), notNullValue());
url2 = element.getAttribute("action");

element = driver.findElement(By.cssSelector("input[type='submit']"));
assertThat(element, notNullValue());
Utils.highlight(element);
requests.clear();
element.submit();
try {
  Thread.sleep(1000);
} catch (InterruptedException e) {
  e.printStackTrace();
}

System.err.println("Captured: ");
requests.keySet().stream().forEach(System.err::println);

this will print:

data:image/png;base64,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
data:image/png;base64,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
data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAEgAAABIAQMAAABvIyEEAAAABlBMVEUAAABTU1OoaSf/AAAAAXRSTlMAQObYZgAAAENJREFUeF7tzbEJACEQRNGBLeAasBCza2lLEGx0CxFGG9hBMDDxRy/72O9FMnIFapGylsu1fgoBdkXfUHLrQgdfrlJN1BdYBjQQm3UAAAAASUVORK5CYII=
https://ps.uci.edu/favicon.ico
https://www.oac.uci.edu/indiv/franklin/cgi-bin/values

the following confirms there is more than one data chunk:

Pattern pattern = Pattern.compile("data:image/png;base64");
System.err.println("Pattern:\n" + pattern.toString());
cnt = 0;
for (String x : requests.keySet()) {
  Matcher matcher = pattern.matcher(x);
  if (matcher.find()) {
    cnt++;
  }
}
assertThat(cnt, greaterThan(1));

the following prints the headers sent to file upload endpoint:

System.err.println("Headers: " + requests.get(url2).toString());

Headers: {
Content-Type=multipart/form-data;
boundary=----WebKitFormBoundaryhsNWaugzUXymNUzV,
Origin=https://ps.uci.edu,
Referer=https://ps.uci.edu/,
Upgrade-Insecure-Requests=1,
User-Agent=Mozilla/5.0 (Windows NT 6.1; WOW64; rv:33.0) Gecko/20120101 Firefox/33.0,
sec-ch-ua="Chromium";v="124",
"Google Chrome";v="124",
"Not-A.Brand";v="99",
sec-ch-ua-mobile=?0,
sec-ch-ua-platform="Linux"
}

Mandatory Flaky Test (Chrome / ChromeDriver Version Gatekeeper)

A common failure mode in Selenium 4 test suites is caused by the independent evolution of:

• Google Chrome (auto-updated by the OS)
• ChromeDriver (pinned in project dependencies or local binaries)

When their major versions diverge, Selenium fails with:

SessionNotCreatedException: "This version of ChromeDriver only supports Chrome version X Current browser version is Y"

This error is catastrophic because it prevents all tests that rely on Chrome or CDP (Chrome DevTools Protocol) from running.

To make this failure predictable and explicit, a gatekeeper test can be introduced that checks versions before constructing ChromeDriver.

---

Gatekeeper Test (BeforeClass)

@BeforeClass
public static void beforeClass() throws Exception {

    String chromeDriverVersion = getChromeDriverVersion(); // chromedriver.exe -version
    String chromeVersion = getInstalledChromeVersion();   // OS-specific discovery without instantiating ChromeDriver

    int driverMajor = parseMajor(chromeDriverVersion);
    int chromeMajor = parseMajor(chromeVersion);

    if (Math.abs(driverMajor - chromeMajor) >= MIN_VERSION_GAP) {
        throw new RuntimeException(
            "Chrome/ChromeDriver major version mismatch: "
            + chromeMajor + " / " + driverMajor);
    }

    // Safe construction only after validation:
    // This is intentional in order to surface any other early exceptions that Selenium
    // or ChromeDriver may introduce in the future (for example, if a previously tolerated
    // version gap suddenly becomes unsupported).

    ChromeDriver driver = null;
    try {
        ChromeOptions options = new ChromeOptions();
        driver = new ChromeDriver(options);
        System.err.println("ChromeDriver instance created safely after version check");
    } catch (SessionNotCreatedException ex) {
        throw new RuntimeException("Fatal Selenium exception: " + ex.getMessage(), ex);
    } finally {
        if (driver != null) {
            driver.quit();
        }
    }
}

@Test
public void test() {
    // Exists only to trigger the run
    System.err.println("Test executed");
}

Observed Non-Deterministic Failures

Despite the simplicity of this logic, the test fails randomly in two distinct ways.

Case 1 — Gatekeeper exception (expected)

RuntimeException: Chrome/ChromeDriver major version mismatch: 145 / 143

Case 2 — Selenium constructor exception (unexpected)

SessionNotCreatedException: Could not start a new session.
This version of ChromeDriver only supports Chrome version 143
Current browser version is 145.0.7632.76
with binary path C:\Program Files\Google\Chrome\Application\chrome.exe

The second failure bypasses the intended gatekeeper logic and originates from:

new ChromeDriver(options);

This exception propagates into all tests that rely on DevTools:

DevTools devTools = ((HasDevTools) driver).getDevTools();
GetVersionResponse response = devTools.send(Browser.getVersion());

and also on less demanding CDP:

driver.executeCdpCommand("Browser.getVersion", new HashMap<>());

Thus, a single version mismatch renders every RPC/CDP-based test unusable.

Root Cause: Constructor Side-Effects and Static Binding

This issue illustrates fundamental Java rules:

Constructors cannot be overridden

Static methods are resolved at compile time

Base class behavior cannot be intercepted polymorphically

Side effects occur before user code regains control

Once new ChromeDriver() is executed, Selenium will:

Spawn chromedriver.exe

Perform protocol handshake

Throw SessionNotCreatedException before any user logic runs

Therefore, post-construction validation is impossible.

This is a textbook example of:

temporal coupling

non-idempotent constructors

side-effect driven initialization

Architectural Warning (Figaro / Barber of Seville Problem)

One must resist the temptation to modify the real base test class (ChromeDriver) to make it “accountable” for discovering version lag.

Doing so risks creating a comic but dangerous situation similar to Figaro, the Barber of Seville — endlessly reacting to failures caused by the very mechanism meant to prevent them.

In other words:

If ChromeDriver itself is responsible for discovering incompatibility

and that discovery requires instantiating ChromeDriver

then the system becomes logically circular

This is a classic case of self-referential failure handling.

Therefore:

Version discovery must be external, static, and side-effect free.

Conclusion

What appears to be a trivial precondition check is complicated by:

Java static dispatch rules

constructor semantics

Selenium’s eager session creation

OS-level process spawning

Chrome auto-updates

The only robust solution is:

Discover Chrome version without interacting with ChromeDriver

Discover chromedriver/chromedriver.exe version via CLI

Compare major versions

Fail early and deterministically

Only then construct ChromeDriver

This prevents:

random ordering failures

flaky CI behavior

mass CDP test collapse

misleading Selenium stack traces

Architectural Warning (Barber of Seville Analogy — Layered Plot Management)

Instead of a purely comic failure loop, this situation resembles the protagonist in The Barber of Seville, who succeeds only by navigating an ever-deepening stack of interdependent plot twists and contingencies.

In software terms, attempting to make the real base class (ChromeDriver) responsible for discovering and correcting its own version incompatibility introduces a layered dependency trap:

The driver must start in order to discover incompatibility

Discovering incompatibility depends on the driver starting

Each new safeguard adds another layer of control logic

This produces a structure of cascading preconditions where failure handling itself becomes part of the failure path.

Such designs tend to evole into systems that require increasing orchestration just to reach a stable state — much like the Barber’s intricate maneuvering through multiple overlapping schemes.

Therefore:

Version discovery must remain external, static, and side-effect free, rather than embedded inside the class whose construction is already fragile.

This keeps responsibility clearly separated:

Gatekeeper logic handles environmental validation

ChromeDriver handles browser automation

Neither must reason about the other’s internal failure modes

This patches the core attitude: “It will break again”

Cultural Analogy: Defensive Engineering (Argentinian Pessimism)

A useful non-software parallel can be drawn from the Argentinian economic mindset shaped by decades of recurring currency and financial crises.

The resulting core attitude is simple:

“It will break again.”

This pessimism is not cynicism; it is adaptive engineering instinct. It leads to designs that assume instability as the default state and prioritize early detection over late recovery.

Applied to Selenium and ChromeDriver version drift, this attitude translates into:

Never trusting that today’s compatible versions will remain compatible tomorrow

Always validating the environment before invoking expensive or fragile operations

Treating external dependencies (browser + driver) as volatile infrastructure, not stable libraries

In practice, this justifies the existence of a gatekeeper test whose only purpose is to fail loudly and deterministically when the environment diverges:

// Safe construction only after validation ChromeDriver driver = new ChromeDriver(options);

The test suite thus encodes institutional memory of past breakages, much like an economy that has learned—through repetition—that collapse is not an anomaly but a recurring event.

Gaming Analogy: The Universal Tool (Crowbar → BFG)

An older gamer analogy helps clarify the engineering instinct behind the gatekeeper test.

In early first-person shooter games, a crude but reliable instrument — often literally a crowbar — served as a universal survival tool. It worked when ammunition ran out, when advanced weapons failed, and when the environment became unpredictable.

By the time of the Doom-era lineage, this evolved into the legendary BFG — not subtle, not elegant, but decisive. Its purpose was not precision, but certainty: when everything else breaks, this still works.

The gatekeeper test plays the same role in a Selenium test suite:

It is intentionally coarse-grained

It does not attempt fine protocol negotiation (RPC vs CDP)

It answers one brutal question only: Is the environment viable or not?

Like the crowbar or the BFG, it is not meant to be pretty — it is meant to prevent the system from wasting hours of effort on doomed execution paths.

This philosophy embraces the defensive maxim:

If the environment is hostile, use the simplest weapon that always fires.

In practice, this means validating Chrome and ChromeDriver compatibility before allowing any higher-level tests to proceed.

Mandatory Flaky Test, Verbose Take

A common error with Selenium 4 testing is due to evolution of the applocation with demnding requirements. A lean tast can be set up to gate keep against the future past lag:

	@BeforeClass
	public static void beforeClass() throws Exception {
		String chromeDriverVersion = getChromeDriverVersion(); // execute chromedriver.exe -version
		String chromeVersion = getInstalledChromeVersion(); // perform OS-specicic version discovery without trying to instanciate ChromeDriver

		int driverMajor = parseMajor(chromeDriverVersion);
		int chromeMajor = parseMajor(chromeVersion);

		if (Math.abs(driverMajor - chromeMajor) >= MIN_VERSION_GAP) {
			throw new RuntimeException(
					"Chrome/ChromeDriver major version mismatch: " + chromeMajor + " / " + driverMajor);
		}

		// 3️⃣ Now safe to construct the driver
		ChromeDriver driver = null;
		try {
			ChromeOptions options = new ChromeOptions();
			driver = new ChromeDriver(options);
			System.err.println("ChromeDriver instance created safely after version check");
		} catch (SessionNotCreatedException ex) {
			// amend exception and propagate
			System.err.println("Fatal Selenium exception: " + ex.getMessage());
			throw new RuntimeException("Fatal Selenium exception: " + ex.getMessage(), ex);
		} finally {
			if (driver != null)
				driver.quit();
		}
	}

	@Test
	public void test() {
    // nothing to do - test method exist solely to trigger the run
		System.err.println("Test executed");
	}

this code despite elementary keeps failing randomly in both

mvn test -Dtest=FailWithSessionNotCreatedTest

Running FailWithSessionNotCreatedTest Gatekeeper: ChromeDriver version: 143.0.7499.42 Gatekeeper: Chrome version: 145.0.7632.76
Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.145 sec
 <<< FAILURE! FailWithSessionNotCreatedTest Time elapsed: 0.144 sec
<<< ERROR! java.lang.RuntimeException: Chrome/ChromeDriver major version mismatch: 145 / 143
``
and
```text
Running FailWithSessionNotCreatedTest Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 3.941 sec
<<< FAILURE! FailWithSessionNotCreatedTest Time elapsed: 3.94 sec
<<< ERROR! org.openqa.selenium.SessionNotCreatedException: Could not start a new session. Response code 500.
Message: session not created: This version of ChromeDriver only supports Chrome version 143 Current browser version is 145.0.7632.76
with binary path C:\Program Files\Google\Chrome\Application\chrome.exe

Host info: host: 'sergueik23', ip: '192.168.12.178'
Build info: version: '4.41.0', revision: '9fc754f'
System info: os.name: 'Windows 10', os.arch: 'amd64', os.version: '10.0', java.version: '11.0.12'
Driver info: org.openqa.selenium.chrome.ChromeDriver
Command: [null, newSession {capabilities=[Capabilities {browserName: chrome, goog:chromeOptions: {args: [], extensions: []}}]}]
        at org.openqa.selenium.remote.ProtocolHandshake.createSession(ProtocolHandshake.java:114)
        at org.openqa.selenium.remote.ProtocolHandshake.createSession(ProtocolHandshake.java:75)
        at org.openqa.selenium.remote.ProtocolHandshake.createSession(ProtocolHandshake.java:61)
        at org.openqa.selenium.remote.HttpCommandExecutor.execute(HttpCommandExecutor.java:195)
        at org.openqa.selenium.remote.service.DriverCommandExecutor.invokeExecute(DriverCommandExecutor.java:216)
        at org.openqa.selenium.remote.service.DriverCommandExecutor.execute(DriverCommandExecutor.java:174)
        at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:604)
        at org.openqa.selenium.remote.RemoteWebDriver.startSession(RemoteWebDriver.java:288)
        at org.openqa.selenium.remote.RemoteWebDriver.<init>(RemoteWebDriver.java:211)
        at org.openqa.selenium.chromium.ChromiumDriver.<init>(ChromiumDriver.java:115)
        at org.openqa.selenium.chrome.ChromeDriver.<init>(ChromeDriver.java:92)
        at org.openqa.selenium.chrome.ChromeDriver.<init>(ChromeDriver.java:76)
        at org.openqa.selenium.chrome.ChromeDriver.<init>(ChromeDriver.java:72)
        at FailWithSessionNotCreatedTest.beforeClass(FailWithSessionNotCreatedTest.java:53)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.base/java.lang.reflect.Method.invoke(Method.java:566)
        at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
        at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
        at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
        at org.junit.internal.runners.statements.RunBefores.invokeMethod(RunBefores.java:33)
        at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24)
        at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
        at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
        at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:252)
        at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:141)
        at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:112)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.base/java.lang.reflect.Method.invoke(Method.java:566)
        at org.apache.maven.surefire.util.ReflectionUtils.invokeMethodWithArray(ReflectionUtils.java:189)
        at org.apache.maven.surefire.booter.ProviderFactory$ProviderProxy.invoke(ProviderFactory.java:165)
        at org.apache.maven.surefire.booter.ProviderFactory.invokeProvider(ProviderFactory.java:85)
        at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:115)
        at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:75)


Results :

Tests in error:
  FailWithSessionNotCreatedTest: Could not start a new session. Response code 500. Message: session not created: This version of ChromeDriver only supports Chrome version 143(..)

the latter exception will affect every RPC rank test operating Chrome browser via

ChromiumDriver driver = new ChromeDriver(options);
DevTools chromeDevTools = ((HasDevTools) driver).getDevTools();
GetVersionResponse response = chromeDevTools.send(Browser.getVersion());

and some (possibly all) tests operarting Chrome via CDP Command:

String command = "Browser.getVersion";
ChromeOptions options = new ChromeOptions();
ChromeDriver driver = new ChromeDriver(options);
Map<String, Object> result = driver.executeCdpCommand(command, new HashMap<>());

Print Mermaid SVG Entirely on the Browser

to run the page in a small web server on the local address from netsh interface ip show address "Wi-Fi" navigate and run

pushd <PROJECT DIRECTORY>
python -m http.server 8000 --bind 192.168.12.122

set HEADLESS=true
mvn test -Dtest=BrowserPrintSvgTest

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.github.sergueik.selenium.BrowserPrintSvgTest
Testing local file: file:/C:/developer/sergueik/selenium_cdp/target/test-classes/svg_test1.html
Raw path: /C:/developer/sergueik/selenium_cdp/target/test-classes/svg_test1.html
Script Console Log: SUCCESS
START
selector=svg#diagram
filename=svg.png
element found
tag=svg
id=diagram
width=600
height=500.0000305175781
serializing
SVG length = 2442
check: <image>: false
check: href: false
check: xlink:href: false
check: url(): true url(#arrowhead)
check: http: true http://www.w3.org/2000/svg
check: https: false
check: data:: false
----- SVG BEGIN -----
<svg id="diagram" width="600px" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 600 500">
  <defs>
    <marker id="arrowhead" markerWidth="10" markerHeight="7" refX="10" refY="3.5" orient="auto">
      <polygon points="0 0, 10 3.5, 0 7" fill="#333"/>
    </marker>
  </defs>

  <!-- Start -->
  <ellipse cx="300" cy="50" rx="80" ry="35" fill="#4CAF50" stroke="#388E3C" stroke-width="2"/>
  <text x="300" y="55" text-anchor="middle" fill="white" font-size="16" font-weight="bold">Start</text>

  <!-- Process 1 -->
  <rect x="200" y="120" width="200" height="60" rx="8" fill="#2196F3" stroke="#1565C0" stroke-width="2"/>
  <text x="300" y="155" text-anchor="middle" fill="white" font-size="14">Process Data</text>

  <!-- Decision -->
  <polygon points="300,220 400,280 300,340 200,280" fill="#FFC107" stroke="#F57F17" stroke-width="2"/>
  <text x="300" y="285" text-anchor="middle" fill="#333" font-size="14">Valid?</text>

  <!-- Process 2 - Yes -->
  <rect x="80" y="370" width="180" height="60" rx="8" fill="#2196F3" stroke="#1565C0" stroke-width="2"/>
  <text x="170" y="405" text-anchor="middle" fill="white" font-size="14">Save Result</text>

  <!-- Process 3 - No -->
  <rect x="340" y="370" width="180" height="60" rx="8" fill="#f44336" stroke="#c62828" stroke-width="2"/>
  <text x="430" y="405" text-anchor="middle" fill="white" font-size="14">Log Error</text>

  <!-- End -->
  <ellipse cx="300" cy="470" rx="80" ry="35" fill="#9C27B0" stroke="#6A1B9A" stroke-width="2"/>
  <text x="300" y="475" text-anchor="middle" fill="white" font-size="16" font-weight="bold">End</text>

  <!-- Arrows -->
  <line x1="300" y1="85" x2="300" y2="120" stroke="#333" stroke-width="2" marker-end="url(#arrowhead)"/>
  <line x1="300" y1="180" x2="300" y2="220" stroke="#333" stroke-width="2" marker-end="url(#arrowhead)"/>
  <line x1="200" y1="280" x2="170" y2="370" stroke="#333" stroke-width="2" marker-end="url(#arrowhead)"/>
  <line x1="400" y1="280" x2="430" y2="370" stroke="#333" stroke-width="2" marker-end="url(#arrowhead)"/>
  <line x1="170" y1="430" x2="270" y2="455" stroke="#333" stroke-width="2" marker-end="url(#arrowhead)"/>
  <line x1="430" y1="430" x2="330" y2="455" stroke="#333" stroke-width="2" marker-end="url(#arrowhead)"/>

  <!-- Labels on arrows -->
  <text x="155" y="325" fill="#388E3C" font-size="13" font-weight="bold">Yes</text>
  <text x="415" y="325" fill="#c62828" font-size="13" font-weight="bold">No</text>
</svg>
----- SVG END -----
blob created, size=2442
object URL created
assigning img.src
img.src assigned
IMAGE ONLOAD
naturalWidth=600
naturalHeight=500
canvas created
canvas context created
drawImage completed
toDataURL completed
PNG length=45134
download link created
download filename=svg.png
download click completed
Continue waiting
Done waiting
output file encoded and added from C:\Users\kouzm\Downloads\svg.png: hash: osFSMvZIbQXNSlnHZQe6e4TK2ngnbpjKyBMLlZCq0E0=
Testing local file: file:/C:/developer/sergueik/selenium_cdp/target/test-classes/svg_test2.html
Raw path: /C:/developer/sergueik/selenium_cdp/target/test-classes/svg_test2.html
Script Console Log: FAIL
START
selector=svg#diagram
filename=svg.png
element found
tag=svg
id=diagram
width=189.82144165039062
height=133.99107360839844
serializing
SVG length = 9675
check: <image>: false
check: href: false
check: xlink:href: false
check: url(): true url(#flowchart-pointEnd)
check: http: true http://www.w3.org/2000/svg
check: https: false
check: data:: false
----- SVG BEGIN -----
<svg width="600px" id="diagram" xmlns="http://www.w3.org/2000/svg" style="max-width: 189.828px; transform: scale(1); transform-origin: 0px 0px;" viewBox="-8 -8 189.828125 134" role="graphics-document document" aria-roledescription="flowchart-v2">
  <style>#graph1{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;fill:#333;}#graph1 .error-icon{fill:#552222;}#graph1 .error-text{fill:#552222;stroke:#552222;}#graph1 .edge-thickness-normal{stroke-width:2px;}#graph1 .edge-thickness-thick{stroke-width:3.5px;}#graph1 .edge-pattern-solid{stroke-dasharray:0;}#graph1 .edge-pattern-dashed{stroke-dasharray:3;}#graph1 .edge-pattern-dotted{stroke-dasharray:2;}#graph1 .marker{fill:#333333;stroke:#333333;}#graph1 .marker.cross{stroke:#333333;}#graph1 svg{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;}#graph1 .label{font-family:"trebuchet ms",verdana,arial,sans-serif;color:#333;}#graph1 .cluster-label text{fill:#333;}#graph1 .cluster-label span{color:#333;}#graph1 .label text,#graph1 span{fill:#333;color:#333;}#graph1 .node rect,#graph1 .node circle,#graph1 .node ellipse,#graph1 .node polygon,#graph1 .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#graph1 .node .label{text-align:center;}#graph1 .node.clickable{cursor:pointer;}#graph1 .arrowheadPath{fill:#333333;}#graph1 .edgePath .path{stroke:#333333;stroke-width:2.0px;}#graph1 .flowchart-link{stroke:#333333;fill:none;}#graph1 .edgeLabel{background-color:#e8e8e8;text-align:center;}#graph1 .edgeLabel rect{opacity:0.5;background-color:#e8e8e8;fill:#e8e8e8;}#graph1 .cluster rect{fill:#ffffde;stroke:#aaaa33;stroke-width:1px;}#graph1 .cluster text{fill:#333;}#graph1 .cluster span{color:#333;}#graph1 div.mermaidTooltip{position:absolute;text-align:center;max-width:200px;padding:2px;font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:12px;background:hsl(80, 100%, 96.2745098039%);border:1px solid #aaaa33;border-radius:2px;pointer-events:none;z-index:100;}#graph1 .flowchartTitleText{text-anchor:middle;font-size:18px;fill:#333;}#graph1 :root{--mermaid-font-family:"trebuchet ms",verdana,arial,sans-serif;}
</style>
  <g>
    <marker id="flowchart-pointEnd" class="marker flowchart" viewBox="0 0 12 20" refX="10" refY="5" markerUnits="userSpaceOnUse" markerWidth="12" markerHeight="12" orient="auto">
      <path d="M 0 0 L 10 5 L 0 10 z" class="arrowMarkerPath" style="stroke-width: 1; stroke-dasharray: 1, 0;"/>
    </marker>
    <marker id="flowchart-pointStart" class="marker flowchart" viewBox="0 0 10 10" refX="0" refY="5" markerUnits="userSpaceOnUse" markerWidth="12" markerHeight="12" orient="auto">
      <path d="M 0 5 L 10 10 L 10 0 z" class="arrowMarkerPath" style="stroke-width: 1; stroke-dasharray: 1, 0;"/>
    </marker>
    <marker id="flowchart-circleEnd" class="marker flowchart" viewBox="0 0 10 10" refX="11" refY="5" markerUnits="userSpaceOnUse" markerWidth="11" markerHeight="11" orient="auto">
      <circle cx="5" cy="5" r="5" class="arrowMarkerPath" style="stroke-width: 1; stroke-dasharray: 1, 0;"/>
    </marker>
    <marker id="flowchart-circleStart" class="marker flowchart" viewBox="0 0 10 10" refX="-1" refY="5" markerUnits="userSpaceOnUse" markerWidth="11" markerHeight="11" orient="auto">
      <circle cx="5" cy="5" r="5" class="arrowMarkerPath" style="stroke-width: 1; stroke-dasharray: 1, 0;"/>
    </marker>
    <marker id="flowchart-crossEnd" class="marker cross flowchart" viewBox="0 0 11 11" refX="12" refY="5.2" markerUnits="userSpaceOnUse" markerWidth="11" markerHeight="11" orient="auto">
      <path d="M 1,1 l 9,9 M 10,1 l -9,9" class="arrowMarkerPath" style="stroke-width: 2; stroke-dasharray: 1, 0;"/>
    </marker>
    <marker id="flowchart-crossStart" class="marker cross flowchart" viewBox="0 0 11 11" refX="-1" refY="5.2" markerUnits="userSpaceOnUse" markerWidth="11" markerHeight="11" orient="auto">
      <path d="M 1,1 l 9,9 M 10,1 l -9,9" class="arrowMarkerPath" style="stroke-width: 2; stroke-dasharray: 1, 0;"/>
    </marker>
    <g class="root">
      <g class="clusters"/>
      <g class="edgePaths">
        <path d="M24.4375,72.78841309823677L28.604166666666668,77.49034424853065C32.770833333333336,82.19227539882452,41.104166666666664,91.59613769941227,49.48046875,96.29806884970613C57.856770833333336,101,66.27604166666667,101,70.48567708333333,101L74.6953125,101" id="L-A-B-0" class=" edge-thickness-normal edge-pattern-solid flowchart-link LS-A LE-B" style="fill:none;" marker-end="url(#flowchart-pointEnd)"/>
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      </g>
      <g class="edgeLabels">
        <g class="edgeLabel">
          <g class="label" transform="translate(0, 0)">
            <foreignObject width="0" height="0">
              <div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; white-space: nowrap;">
                <span class="edgeLabel">
</span>
              </div>
            </foreignObject>
          </g>
        </g>
        <g class="edgeLabel">
          <g class="label" transform="translate(0, 0)">
            <foreignObject width="0" height="0">
              <div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; white-space: nowrap;">
                <span class="edgeLabel">
</span>
              </div>
            </foreignObject>
          </g>
        </g>
        <g class="edgeLabel">
          <g class="label" transform="translate(0, 0)">
            <foreignObject width="0" height="0">
              <div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; white-space: nowrap;">
                <span class="edgeLabel">
</span>
              </div>
            </foreignObject>
          </g>
        </g>
        <g class="edgeLabel">
          <g class="label" transform="translate(0, 0)">
            <foreignObject width="0" height="0">
              <div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; white-space: nowrap;">
                <span class="edgeLabel">
</span>
              </div>
            </foreignObject>
          </g>
        </g>
      </g>
      <g class="nodes">
        <g class="node default default" id="flowchart-A-24" transform="translate(12.21875, 59)">
          <rect class="basic label-container" style="" rx="0" ry="0" x="-12.21875" y="-17" width="24.4375" height="34"/>
          <g class="label" style="" transform="translate(-4.71875, -9.5)">
            <foreignObject width="9.4375" height="19">
              <div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; white-space: nowrap;">
                <span class="nodeLabel">A
</span>
              </div>
            </foreignObject>
          </g>
        </g>
        <g class="node default default" id="flowchart-B-25" transform="translate(86.7265625, 101)">
          <rect class="basic label-container" style="" rx="0" ry="0" x="-12.03125" y="-17" width="24.0625" height="34"/>
          <g class="label" style="" transform="translate(-4.53125, -9.5)">
            <foreignObject width="9.0625" height="19">
              <div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; white-space: nowrap;">
                <span class="nodeLabel">B
</span>
              </div>
            </foreignObject>
          </g>
        </g>
        <g class="node default default" id="flowchart-C-26" transform="translate(86.7265625, 17)">
          <rect class="basic label-container" style="" rx="0" ry="0" x="-12.2890625" y="-17" width="24.578125" height="34"/>
          <g class="label" style="" transform="translate(-4.7890625, -9.5)">
            <foreignObject width="9.578125" height="19">
              <div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; white-space: nowrap;">
                <span class="nodeLabel">C
</span>
              </div>
            </foreignObject>
          </g>
        </g>
        <g class="node default default" id="flowchart-D-27" transform="translate(161.421875, 59)">
          <rect class="basic label-container" style="" rx="0" ry="0" x="-12.40625" y="-17" width="24.8125" height="34"/>
          <g class="label" style="" transform="translate(-4.90625, -9.5)">
            <foreignObject width="9.8125" height="19">
              <div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; white-space: nowrap;">
                <span class="nodeLabel">D
</span>
              </div>
            </foreignObject>
          </g>
        </g>
      </g>
    </g>
  </g>
</svg>
----- SVG END -----
blob created, size=9675
object URL created
assigning img.src
img.src assigned
IMAGE ONLOAD
naturalWidth=600
naturalHeight=424
canvas created
canvas context created
drawImage completed
ONLOAD ERROR
SecurityError
Failed to execute 'toDataURL' on 'HTMLCanvasElement': Tainted canvases may not be exported.
Continue waiting
Continue waiting
Continue waiting
Continue waiting
Timed out waiting for file
Testing local file: file:/C:/developer/sergueik/selenium_cdp/target/test-classes/svg_test3.html
Raw path: /C:/developer/sergueik/selenium_cdp/target/test-classes/svg_test3.html
Script Console Log: SUCCESS
START
selector=svg#diagram
filename=svg.png
element found
tag=svg
id=diagram
width=600
height=150
serializing
SVG length = 88
check: <image>: false
check: href: false
check: xlink:href: false
check: url(): false
check: http: true http://www.w3.org/2000/svg
check: https: false
check: data:: false
----- SVG BEGIN -----
<svg xmlns="http://www.w3.org/2000/svg" width="600px" id="diagram" src="flowchart.svg"/>
----- SVG END -----
blob created, size=88
object URL created
assigning img.src
img.src assigned
IMAGE ONLOAD
naturalWidth=600
naturalHeight=150
canvas created
canvas context created
drawImage completed
toDataURL completed
PNG length=3314
download link created
download filename=svg.png
download click completed
Continue waiting
Done waiting
output file encoded and added from C:\Users\kouzm\Downloads\svg.png: hash: e7Jn+2V6VQ+c791XFZelruhI56Zjl1xVFFrbPlLrT0E=
This is a blank PNG
Tests run: 5, Failures: 0, Errors: 0, Skipped: 2, Time elapsed: 49.615 sec

Results :

Tests run: 5, Failures: 0, Errors: 0, Skipped: 2

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  01:09 min
[INFO] Finished at: 2026-09-26T00:23:22-04:00
[INFO] -----------------------------------------

inline Mermaid SVG
        ↓
serialize
        ↓
Blob
        ↓
Image.onload       ✓
        ↓
Canvas.drawImage   ✓
        ↓
canvas.toDataURL   ✗  SecurityError: tainted canvas

canvas has become tainted

NOTE: the noop test and test with vanilla svg embedded in HTML both passed.

to disable IPV6:

reg.exe add "HKLM\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters" ^
    /v DisabledComponents ^
    /t REG_DWORD ^
    /d 0xFF ^
    /f

The first image is not merely "poorly rendered Mermaid." It is essentially Mermaid's SVG with its stylesheet not being applied.

Compare the symptoms:

rectangles are solid black → SVG's default fill for is black labels are absent → the styling/foreign-object presentation isn't being applied correctly curved connecting paths are absent → an SVG with no applicable stroke has no visible line; its default fill doesn't produce a visible open curve arrowheads remain → the marker-end="url(#...)" definitions are still being resolved and rendered

The second screenshot is the normal Mermaid result: CSS supplies the node fill/stroke, path stroke, fonts, etc.

So this is a very useful distinction:

Mermaid SVG
    |
    +-- SVG geometry works
    |      |
    |      +-- rects appear
    |      +-- marker references work
    |
    +-- Mermaid CSS presentation does NOT work
           |
           +-- node fill/stroke missing
           +-- path stroke missing
           +-- label presentation missing

this was produced by adding the style="fill: red; stroke: blue; stroke-width: 2px;" in the <svg> element:

<g class="node default default" id="flowchart-B-25" transform="translate(86.7265625, 101)">
  <rect class="basic label-container" style="fill: red; stroke: blue; stroke-width: 2px;" rx="0" ry="0" x="-12.03125" y="-17" width="24.0625" height="34"/>
  <g class="label" style="" transform="translate(-4.53125, -9.5)">
    <foreignObject width="9.0625" height="19">
      <div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; white-space: nowrap;">
        <span class="nodeLabel">B
</span>
      </div>
    </foreignObject>
  </g>
</g>

Underlying Mechanics

There isn't Java class/method that appends the callback: it's provisioned by the WebDriver remote end (the browser driver) according to the W3C WebDriver specification

@Override
public Object executeAsyncScript(String script, Object... args) {
  List<Object> convertedArgs =
      Stream.of(args)
          .map(new WebElementToJsonConverter())
          .collect(Collectors.toList());

  return execute(
      DriverCommand.EXECUTE_ASYNC_SCRIPT(script, convertedArgs))
      .getValue();
}

NOTE: there is no args.add(callback) here. the Selenium client constructs the HTTP/WebDriver command containing:

{
  "script": "...",
  "args": [...]
}

The W3C WebDriver spec's Execute Async Script algorithm explicitly says:

• Let body and arguments be ... ...

• Run the following substeps in parallel:

  • Append resolve to script arguments.
  • Let result be the result of promise-calling execute a function body, with arguments body and arguments.

That Append resolve to script arguments is the critical operation.

executeAsyncScript(script, arg1, arg2)

             ↓

Selenium Java client:
    POST /session/.../execute/async
    {
        script: script,
        args: [arg1, arg2]
    }

             ↓

browser driver / WebDriver remote end:

 arguments = [arg1, arg2]

    append(callback)

    arguments = [arg1, arg2, callback]

             ↓

    execute function body with those arguments

The current WebDriver specification describes this explicitly: the async command supplies an additional argument as the final argument to the function.

And an older WebDriver specification makes the operation even more visually obvious:

• Let callback be a function
• Append callback to arguments
• Let result be the result of calling execute a function body with arguments body and arguments

How it happen - Here are three different pieces, and they live in different places:

Layer	Where	What
Java Selenium	RemoteWebDriver.executeAsyncScript()	Sends script + caller's args
WebDriver protocol	W3C Execute Async Script algorithm	Appends callback to arguments
Browser-specific driver	ChromeDriver or other	Implements that remote-end algorithm

The Selenium Java client does not append the callback. RemoteWebDriver.executeAsyncScript() sends the supplied argument list unchanged The WebDriver remote end then appends a completion callback as the final argument before invoking the JavaScript function.

is much more precise than an "Selenium injects a callback"

And it explains perfectly why this works:

var done = arguments[arguments.length - 1];

because the protocol guarantees that the final argument is the WebDriver completion callback.

an early WebDriver specification actually contains almost the exact pseudo-code you were looking for — Append callback to arguments

NOTE: the executeAsyncScript does not return when the JavaScript function returns; it returns when the WebDriver-injected completion callback is invoked

   var done = arguments[arguments.length - 1];
			// `done` argument is not supplied by the Java caller explicitly 
			// it is the WebDriver-provided completion callback, injected as the final argument of the JavaScript function invocation. 
			// the first value passed to done(...)
			// done(status + "\n" + trace.join("\n"))
			// becomes the return value of executeAsyncScript(...)
			// There isn't Java class/method that appends the callback: 
			// it's provisioned by the WebDriver remote end (the browser driver) according to the W3C WebDriver specification:

see also: https://github.com/SeleniumHQ/selenium/blob/trunk/java/src/org/openqa/selenium/remote/RemoteWebDriver.java

@Override
public Object executeAsyncScript(String script, Object... args) {
  List<Object> convertedArgs = Stream.of(args)
    .map(new WebElementToJsonConverter())
    .collect(Collectors.toList());

  return execute( DriverCommand.EXECUTE_ASYNC_SCRIPT(script, convertedArgs).getValue();
}

See Also

• chrome devtools project

• puppeteer online

• GoogleChrome/puppeteer

• ChromeDevTools/debugger-protocol-viewer

• standalond java cdp client (commecial)

• cdp4j/javadoc

• headless chrome devtools based testing lecture and video(in Russan)

• HTML to PDF conversion with Chromium devtools and Selenium Python client (in Russan)

• PDF configuration with Puppeteer

• Selenium 4 Relative Locator DOM traversal DSL.

• Selenium 4 Relatve locator examples

• alternative java websocket client HubSpot/ChromeDevToolsClient for the Chrome DevTools Protocol

• another chrome-devtools-java-client project featuring annotation-style builder pattern design for handling chrome commandline arguments.

• examples with callback hook example

• yet another project chrome-devtools-webdriver-integration

• yet another framework project sachinguptait/SeleniumAutomation demonstrating Selenium 4 and CDP features

• yet another project SrinivasanTarget/selenium4CDPsamples

• Python Chrome Devtools Procotol client

• yet another CDP Java client . Note: only works with Selenium 4.alpha-2

• Python Chrome Devtools Procotol client

• Selenium 3.x CDP Exender clone project - the original project sahajamit/chrome-devtools-webdriver-integration - is somewhat stale

• Selenium 4.0x WindowType feature

• use CDP to switch to winows stackoverflow

• JavaScript-style event callback design jpuppeteer

• library inspired by Puppeteer to facilitate the use of Chrome DevTools API to control Chrome or Chromium via Java

• advanced prevention headless browser detection

• recaptcha-3 score

• Puppeteer Documentation

• difference between WebDriver and DevTool protocol explained

• using Chrome DevTools Protocol

• overview of DevTools access offered by Selenium 4

• Libraries.io - monitors over 2 million open source libraries/packages from 36 package managers

• collection of Selenium 4 CDP-specific tests

• https://medium.com/codex/selenium4-a-peek-into-chrome-devtools-92bca6de55e0

• BiDirectional WebDriver Protocol w3c spec

• BiDi - The future of cross-browser automation blog

• BiDirectional functionality official documentation

• list of bidi APIs examples

• guide To Java 8 Optional

• translation of the guide To Java 8 Optional(in Russian)

• Ferrum - Ruby gem for "high-level" API for CDP backed Chrome browser automation rubycdp/ferrum repository, rubygems.org link documentation translation (in Russian)

• serg-ty/selenium-tests-logger project to enable listeners as part of the logging

• list of existing headless web browsers

• new headless mode

• interactive performance analysis with Chrome DevTools

• replacing request url, postdata and headers

• getting connection information and cookies from chrome dev tools and use with curl

• How to Install Google Chrome Web Browser on Ubuntu 18.04

• Content Security Policy (CSP) Evaluator

• Testing for Content Security Policy

• Enable page Content Security Policy by-passing

• Content Security Policy Examples

• Simple Push Demo page and sources

• https://jakearchibald.github.io/isserviceworkerready/demos/sync/

• https://developer.chrome.com/docs/devtools/javascript/background-services

• https://github.com/WebMCP-org/chrome-devtools-quickstart

• https://www.datacamp.com/tutorial/webmcp-tutorial

• https://developer.chrome.com/docs/ai/webmcp

• https://qaskills.sh/blog/selenium-cdp-add-script-evaluate-guide (pythonish - not callable)

License

This project is licensed under the terms of the MIT license.

Author

Serguei Kouzmine