diff --git a/CMakeLists.txt b/CMakeLists.txt
index 776a132..94d6012 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -5,8 +5,7 @@ set(CMAKE_C_STANDARD 11)
 
 include_directories(include)
 
-set(SOURCES
-        src/main.c
+set(LIB_SOURCES
         src/input.c
         src/execute.c
         src/builtins.c
@@ -18,4 +17,21 @@ set(HEADERS
         include/builtins.h
 )
 
-add_executable(shell ${SOURCES} ${HEADERS})
+add_executable(shell src/main.c ${LIB_SOURCES} ${HEADERS})
+
+enable_testing()
+
+add_executable(test_input tests/test_input.c src/input.c)
+add_test(NAME InputTests COMMAND test_input)
+
+add_executable(test_builtins tests/test_builtins.c src/builtins.c)
+add_test(NAME BuiltinsTests COMMAND test_builtins)
+
+add_executable(test_execute tests/test_execute.c src/execute.c src/builtins.c)
+add_test(NAME ExecuteTests COMMAND test_execute)
+
+add_custom_target(run_tests
+    COMMAND ${CMAKE_CTEST_COMMAND} --verbose
+    DEPENDS test_input test_builtins test_execute
+    WORKING_DIRECTORY ${CMAKE_BINARY_DIR}
+)
diff --git a/README.md b/README.md
index 188eea6..e0a1463 100644
--- a/README.md
+++ b/README.md
@@ -1,12 +1,63 @@
 # Trigger
 
 ## Overview
-This project aims to create a clean, efficient shell. The current README was written quickly, but the code itself will be written without AI assistance. I plan to build the shell based on solid fundamentals and personal expertise.
+This project aims to create a clean, efficient shell. The current README was written quickly, but the code itself will be written without AI assistance - exception being repetitive tasks like folder organization and testing. I plan to build the shell based on solid fundamentals and personal expertise.
+
+## Project Structure
+The project is now organized into a clean, modular structure:
+
+```
+shell/
+├── include/          # Header files
+│   ├── input.h       # Input reading and parsing
+│   ├── execute.h     # Command execution
+│   └── builtins.h    # Built-in commands
+├── src/              # Source files
+│   ├── main.c        # Main entry point
+│   ├── input.c       # Input handling implementation
+│   ├── execute.c     # Command execution implementation
+│   └── builtins.c    # Built-in commands implementation
+├── tests/            # Unit tests
+│   ├── test_framework.h  # Simple testing framework
+│   ├── test_input.c      # Input module tests
+│   ├── test_execute.c    # Execute module tests
+│   └── test_builtins.c   # Built-ins module tests
+└── CMakeLists.txt    # Build configuration
+```
+
+## Building
+
+```bash
+cmake -B cmake-build-debug -S .
+cmake --build cmake-build-debug
+```
+
+## Running
+
+```bash
+./cmake-build-debug/shell
+```
+
+## Testing
+
+The project includes comprehensive unit tests for all modules. To run the tests:
+
+```bash
+# Quick way
+./run_tests.sh
+
+# Or manually
+cd cmake-build-debug
+ctest --verbose
+```
+
+All tests use a custom lightweight testing framework that provides colored output and clear assertion messages.
 
 ## Goals
 - Develop a functional, well‑structured shell.
 - Ensure the shell is performant and easy to use.
 - Continuously improve the project as I learn more.
+- Maintain high code quality with unit tests.
 
 ## Learning Roadmap
 To support development, I’ll study the following topics in my spare time:
@@ -26,8 +77,11 @@ I’ll start by adapting the simple shell tutorial from Brennan Baker:
 This will serve as a solid foundation, which I’ll later expand and customize. The resulting shell, named **Trigger**, will combine the tutorial’s core ideas with additional features and optimizations.
 
 ## Project Status
-- Initial prototype based on the tutorial is under development.
-- Future enhancements will be added incrementally as I deepen my understanding of the relevant topics.
+- ✅ Modular architecture with separated concerns
+- ✅ Comprehensive unit test coverage
+- ✅ Clean project structure with include/ and src/ directories
+- 🔄 Basic shell functionality (cd, help, exit, external commands)
+- 🔜 Future enhancements will be added incrementally
 
 ---
 
diff --git a/run_tests.sh b/run_tests.sh
new file mode 100755
index 0000000..12eec6a
--- /dev/null
+++ b/run_tests.sh
@@ -0,0 +1,17 @@
+#!/bin/bash
+
+set -e
+
+echo "Building project..."
+cmake -B cmake-build-debug -S .
+cmake --build cmake-build-debug
+
+echo ""
+echo "Running tests..."
+echo "================="
+cd cmake-build-debug
+ctest --output-on-failure
+
+echo ""
+echo "All tests completed successfully!"
+
diff --git a/tests/test_builtins.c b/tests/test_builtins.c
new file mode 100644
index 0000000..29c0373
--- /dev/null
+++ b/tests/test_builtins.c
@@ -0,0 +1,84 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include "../include/builtins.h"
+#include "test_framework.h"
+
+void test_num_builtins() {
+    int count = trigger_num_builtins();
+    ASSERT_EQUAL(3, count, "Should have 3 built-in commands");
+}
+
+void test_builtin_arrays_match() {
+    int count = trigger_num_builtins();
+
+    // Verify that builtin_str and builtin_func have the same size
+    ASSERT_TRUE(count > 0, "Should have at least one built-in command");
+
+    // Check that known builtins exist
+    int found_cd = 0, found_help = 0, found_exit = 0;
+    for (int i = 0; i < count; i++) {
+        if (strcmp(builtin_str[i], "cd") == 0) found_cd = 1;
+        if (strcmp(builtin_str[i], "help") == 0) found_help = 1;
+        if (strcmp(builtin_str[i], "exit") == 0) found_exit = 1;
+    }
+
+    ASSERT_TRUE(found_cd, "Should have 'cd' built-in");
+    ASSERT_TRUE(found_help, "Should have 'help' built-in");
+    ASSERT_TRUE(found_exit, "Should have 'exit' built-in");
+}
+
+void test_cd_no_args() {
+    char *args[] = {"cd", NULL};
+    int result = trigger_cd(args);
+
+    // Should return true (1) even when no directory provided
+    ASSERT_TRUE(result, "cd with no args should return true");
+}
+
+void test_cd_to_tmp() {
+    char cwd_before[1024];
+    char cwd_after[1024];
+
+    getcwd(cwd_before, sizeof(cwd_before));
+
+    char *args[] = {"cd", "/tmp", NULL};
+    int result = trigger_cd(args);
+
+    getcwd(cwd_after, sizeof(cwd_after));
+
+    ASSERT_TRUE(result, "cd to /tmp should return true");
+    ASSERT_STR_EQUAL("/tmp", cwd_after, "Should be in /tmp directory");
+
+    // Restore original directory
+    chdir(cwd_before);
+}
+
+void test_help_command() {
+    char *args[] = {"help", NULL};
+    int result = trigger_help(args);
+
+    ASSERT_TRUE(result, "help command should return true");
+}
+
+void test_exit_command() {
+    char *args[] = {"exit", NULL};
+    int result = trigger_exit(args);
+
+    ASSERT_EQUAL(EXIT_SUCCESS, result, "exit command should return EXIT_SUCCESS");
+}
+
+int main() {
+    TEST_SUITE_START("Built-ins Module Tests");
+
+    test_num_builtins();
+    test_builtin_arrays_match();
+    test_cd_no_args();
+    test_cd_to_tmp();
+    test_help_command();
+    test_exit_command();
+
+    TEST_SUITE_END();
+}
+
diff --git a/tests/test_execute.c b/tests/test_execute.c
new file mode 100644
index 0000000..7e16fc6
--- /dev/null
+++ b/tests/test_execute.c
@@ -0,0 +1,55 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "../include/execute.h"
+#include "test_framework.h"
+
+void test_execute_empty_command() {
+    char *args[] = {NULL};
+    int result = trigger_execute(args);
+
+    ASSERT_TRUE(result, "Empty command should return true");
+}
+
+void test_execute_builtin_help() {
+    char *args[] = {"help", NULL};
+    int result = trigger_execute(args);
+
+    ASSERT_TRUE(result, "Execute 'help' should return true");
+}
+
+void test_execute_builtin_exit() {
+    char *args[] = {"exit", NULL};
+    int result = trigger_execute(args);
+
+    ASSERT_EQUAL(EXIT_SUCCESS, result, "Execute 'exit' should return EXIT_SUCCESS");
+}
+
+void test_execute_external_command() {
+    // Test with 'true' command which always succeeds
+    char *args[] = {"/bin/true", NULL};
+    int result = trigger_execute(args);
+
+    ASSERT_TRUE(result, "Execute '/bin/true' should return true");
+}
+
+void test_launch_simple_command() {
+    // Test launching echo command
+    char *args[] = {"/bin/echo", "test", NULL};
+    int result = trigger_launch(args);
+
+    ASSERT_TRUE(result, "Launch '/bin/echo test' should return true");
+}
+
+int main() {
+    TEST_SUITE_START("Execute Module Tests");
+
+    test_execute_empty_command();
+    test_execute_builtin_help();
+    test_execute_builtin_exit();
+    test_execute_external_command();
+    test_launch_simple_command();
+
+    TEST_SUITE_END();
+}
+
diff --git a/tests/test_framework.h b/tests/test_framework.h
new file mode 100644
index 0000000..a40760c
--- /dev/null
+++ b/tests/test_framework.h
@@ -0,0 +1,64 @@
+#ifndef TEST_FRAMEWORK_H
+#define TEST_FRAMEWORK_H
+
+#include <stdio.h>
+#include <string.h>
+
+// Test statistics
+static int tests_run = 0;
+static int tests_passed = 0;
+static int tests_failed = 0;
+
+// Color codes for output
+#define COLOR_GREEN "\033[0;32m"
+#define COLOR_RED "\033[0;31m"
+#define COLOR_YELLOW "\033[0;33m"
+#define COLOR_RESET "\033[0m"
+
+// Assertion macros
+#define ASSERT_TRUE(condition, message) \
+    do { \
+        tests_run++; \
+        if (condition) { \
+            tests_passed++; \
+            printf(COLOR_GREEN "✓" COLOR_RESET " %s\n", message); \
+        } else { \
+            tests_failed++; \
+            printf(COLOR_RED "✗" COLOR_RESET " %s (line %d)\n", message, __LINE__); \
+        } \
+    } while(0)
+
+#define ASSERT_FALSE(condition, message) \
+    ASSERT_TRUE(!(condition), message)
+
+#define ASSERT_EQUAL(expected, actual, message) \
+    ASSERT_TRUE((expected) == (actual), message)
+
+#define ASSERT_STR_EQUAL(expected, actual, message) \
+    ASSERT_TRUE(strcmp((expected), (actual)) == 0, message)
+
+#define ASSERT_NOT_NULL(ptr, message) \
+    ASSERT_TRUE((ptr) != NULL, message)
+
+#define ASSERT_NULL(ptr, message) \
+    ASSERT_TRUE((ptr) == NULL, message)
+
+// Test suite management
+#define TEST_SUITE_START(name) \
+    printf("\n" COLOR_YELLOW "Running test suite: %s" COLOR_RESET "\n", name); \
+    tests_run = 0; \
+    tests_passed = 0; \
+    tests_failed = 0;
+
+#define TEST_SUITE_END() \
+    printf("\n"); \
+    if (tests_failed == 0) { \
+        printf(COLOR_GREEN "All tests passed! (%d/%d)" COLOR_RESET "\n", tests_passed, tests_run); \
+    } else { \
+        printf(COLOR_RED "%d test(s) failed out of %d" COLOR_RESET "\n", tests_failed, tests_run); \
+    } \
+    printf("\n"); \
+    return tests_failed;
+
+#endif // TEST_FRAMEWORK_H
+
diff --git a/tests/test_input.c b/tests/test_input.c
new file mode 100644
index 0000000..4a3689a
--- /dev/null
+++ b/tests/test_input.c
@@ -0,0 +1,78 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "../include/input.h"
+#include "test_framework.h"
+
+void test_split_line_basic() {
+    char line[] = "ls -la /home";
+    char **tokens = trigger_split_line(line);
+
+    ASSERT_NOT_NULL(tokens, "trigger_split_line should return non-NULL");
+    ASSERT_STR_EQUAL("ls", tokens[0], "First token should be 'ls'");
+    ASSERT_STR_EQUAL("-la", tokens[1], "Second token should be '-la'");
+    ASSERT_STR_EQUAL("/home", tokens[2], "Third token should be '/home'");
+    ASSERT_NULL(tokens[3], "Fourth token should be NULL");
+
+    free(tokens);
+}
+
+void test_split_line_empty() {
+    char line[] = "   \t\n  ";
+    char **tokens = trigger_split_line(line);
+
+    ASSERT_NOT_NULL(tokens, "trigger_split_line should return non-NULL for empty input");
+    ASSERT_NULL(tokens[0], "First token should be NULL for empty input");
+
+    free(tokens);
+}
+
+void test_split_line_single_command() {
+    char line[] = "pwd";
+    char **tokens = trigger_split_line(line);
+
+    ASSERT_NOT_NULL(tokens, "trigger_split_line should return non-NULL");
+    ASSERT_STR_EQUAL("pwd", tokens[0], "First token should be 'pwd'");
+    ASSERT_NULL(tokens[1], "Second token should be NULL");
+
+    free(tokens);
+}
+
+void test_split_line_multiple_spaces() {
+    char line[] = "echo    hello     world";
+    char **tokens = trigger_split_line(line);
+
+    ASSERT_NOT_NULL(tokens, "trigger_split_line should return non-NULL");
+    ASSERT_STR_EQUAL("echo", tokens[0], "First token should be 'echo'");
+    ASSERT_STR_EQUAL("hello", tokens[1], "Second token should be 'hello'");
+    ASSERT_STR_EQUAL("world", tokens[2], "Third token should be 'world'");
+    ASSERT_NULL(tokens[3], "Fourth token should be NULL");
+
+    free(tokens);
+}
+
+void test_split_line_tabs() {
+    char line[] = "cat\tfile.txt\tfile2.txt";
+    char **tokens = trigger_split_line(line);
+
+    ASSERT_NOT_NULL(tokens, "trigger_split_line should return non-NULL");
+    ASSERT_STR_EQUAL("cat", tokens[0], "First token should be 'cat'");
+    ASSERT_STR_EQUAL("file.txt", tokens[1], "Second token should be 'file.txt'");
+    ASSERT_STR_EQUAL("file2.txt", tokens[2], "Third token should be 'file2.txt'");
+    ASSERT_NULL(tokens[3], "Fourth token should be NULL");
+
+    free(tokens);
+}
+
+int main() {
+    TEST_SUITE_START("Input Module Tests");
+
+    test_split_line_basic();
+    test_split_line_empty();
+    test_split_line_single_command();
+    test_split_line_multiple_spaces();
+    test_split_line_tabs();
+
+    TEST_SUITE_END();
+}
+