diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
new file mode 100644
index 0000000..5397f59
--- /dev/null
+++ b/.github/workflows/tests.yml
@@ -0,0 +1,38 @@
+name: Tests
+
+on:
+  push:
+    branches: [ main, develop ]
+  pull_request:
+    branches: [ main, develop ]
+
+jobs:
+  test:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest]
+        php: ['7.4', '8.0', '8.1', '8.2', '8.3', '8.4', '8.5']
+        
+    name: PHP ${{ matrix.php }} - ${{ matrix.os }}
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v4
+
+    - name: Setup PHP
+      uses: shivammathur/setup-php@v2
+      with:
+        php-version: ${{ matrix.php }}
+        extensions: dom, curl, libxml, mbstring, zip
+        coverage: none
+
+    - name: Install xmlstarlet
+      run: sudo apt-get update && sudo apt-get install -y xmlstarlet
+
+    - name: Install dependencies
+      run: composer update --prefer-dist --no-progress
+
+    - name: Run test suite
+      run: ./vendor/bin/phpunit --testdox
diff --git a/.github/workflows/update-changelog.yml b/.github/workflows/update-changelog.yml
new file mode 100644
index 0000000..277821c
--- /dev/null
+++ b/.github/workflows/update-changelog.yml
@@ -0,0 +1,32 @@
+name: "Update Changelog"
+
+on:
+  release:
+    types: [released]
+
+permissions:
+  contents: write
+
+jobs:
+  update:
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v5
+        with:
+          ref: main
+
+      - name: Update Changelog
+        uses: stefanzweifel/changelog-updater-action@v1
+        with:
+          latest-version: ${{ github.event.release.name }}
+          release-notes: ${{ github.event.release.body }}
+
+      - name: Commit updated CHANGELOG
+        uses: stefanzweifel/git-auto-commit-action@v7
+        with:
+          branch: main
+          commit_message: Update CHANGELOG
+          file_pattern: CHANGELOG.md
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..dddbc6a
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+vendor
+.phpunit.cache
+composer.lock
diff --git a/README.md b/README.md
index 3635a44..ba6b668 100644
--- a/README.md
+++ b/README.md
@@ -30,6 +30,16 @@ For XmlStarlet on other platforms, see [here](http://xmlstar.sourceforge.net/doc
 ./vendor/bin/phpunit-failed-runner
 ```
 
+## Testing
+
+This package includes a comprehensive test suite that demonstrates the incremental test-fixing workflow.
+
+Run the test suite:
+
+```bash
+composer test
+```
+
 ### Changelog
 
 Please see [CHANGELOG](CHANGELOG.md) for more information what has changed recently.
diff --git a/bin/phpunit-failed-runner b/bin/phpunit-failed-runner
index 564a529..7bc4eb4 100755
--- a/bin/phpunit-failed-runner
+++ b/bin/phpunit-failed-runner
@@ -8,10 +8,22 @@ else
     runner="./vendor/bin/phpunit"
 fi
 
+# Determine XSL path - check if we're in the package itself or using it as a dependency
+if [ -f "./prune.xsl" ]; then
+    # We're in the package root
+    xsl_path="."
+elif [ -f "./vendor/chrisdicarlo/phpunit-failed-runner/prune.xsl" ]; then
+    # We're using the package as a dependency
+    xsl_path="./vendor/chrisdicarlo/phpunit-failed-runner"
+else
+    echo "Error: Cannot find XSL transformation files"
+    exit 1
+fi
+
 if test -f "$logfile"; then
     echo -e "Logfile found. Searching for previously failing tests... \U23F3"
 
-    count_failed_tests="$(xmlstarlet tr ./vendor/chrisdicarlo/phpunit-failed-runner/prune.xsl junit.xml | xmlstarlet tr --omit-decl ./vendor/chrisdicarlo/phpunit-failed-runner/count-failed.xsl)"
+    count_failed_tests="$(xmlstarlet tr "$xsl_path/prune.xsl" junit.xml | xmlstarlet tr --omit-decl "$xsl_path/count-failed.xsl")"
 
     if [ "$count_failed_tests" = "0" ]; then
         echo -e "No failed tests! Great job! \U1F44D \U1F389"
@@ -19,7 +31,7 @@ if test -f "$logfile"; then
         exit 0
     else
         echo -e "Found $count_failed_tests previously failing tests, filtering... \U1F97A"
-        filter=$(xmlstarlet tr ./vendor/chrisdicarlo/phpunit-failed-runner/prune.xsl junit.xml | xmlstarlet tr --omit-decl ./vendor/chrisdicarlo/phpunit-failed-runner/failed-tests.xsl); "$runner" --filter "$filter" --log-junit junit.xml
+        filter=$(xmlstarlet tr "$xsl_path/prune.xsl" junit.xml | xmlstarlet tr --omit-decl "$xsl_path/failed-tests.xsl"); "$runner" --filter "$filter" --log-junit junit.xml
     fi
 else
     echo -e "Logfile not found. Running the test suite... \U1F91E"
@@ -29,7 +41,7 @@ else
 fi
 
 if test -f "$logfile"; then
-    count_failed_tests="$(xmlstarlet tr ./vendor/chrisdicarlo/phpunit-failed-runner/prune.xsl junit.xml | xmlstarlet tr --omit-decl ./vendor/chrisdicarlo/phpunit-failed-runner/count-failed.xsl)"
+    count_failed_tests="$(xmlstarlet tr "$xsl_path/prune.xsl" junit.xml | xmlstarlet tr --omit-decl "$xsl_path/count-failed.xsl")"
 
     if [ "$count_failed_tests" = "0" ]; then
         echo -e "No failed tests! Great job! \U1F44D \U1F389"
diff --git a/composer.json b/composer.json
index dc23a5c..b5986dd 100644
--- a/composer.json
+++ b/composer.json
@@ -19,5 +19,16 @@
     ],
     "bin": [
         "bin/phpunit-failed-runner"
-    ]
+    ],
+    "require-dev": {
+        "phpunit/phpunit": "^8.5|^9.6|^10.5|^11.0"
+    },
+    "autoload-dev": {
+        "psr-4": {
+            "Tests\\": "tests/"
+        }
+    },
+    "scripts": {
+        "test": "phpunit"
+    }
 }
diff --git a/phpunit-integration-fixtures.xml b/phpunit-integration-fixtures.xml
new file mode 100644
index 0000000..cbd0c63
--- /dev/null
+++ b/phpunit-integration-fixtures.xml
@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.5/phpunit.xsd"
+         bootstrap="vendor/autoload.php"
+         colors="true"
+         failOnRisky="true"
+         failOnWarning="true"
+         cacheDirectory=".phpunit.cache">
+    <testsuites>
+        <testsuite name="Fixture Tests for Integration Testing">
+            <file>tests/AlwaysPassingTest.php</file>
+            <file>tests/InitiallyFailingTest.php</file>
+            <file>tests/AnotherFailingTest.php</file>
+        </testsuite>
+    </testsuites>
+    <source>
+        <include>
+            <directory>bin</directory>
+        </include>
+    </source>
+</phpunit>
diff --git a/phpunit.xml b/phpunit.xml
new file mode 100644
index 0000000..fede57b
--- /dev/null
+++ b/phpunit.xml
@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.5/phpunit.xsd"
+         bootstrap="vendor/autoload.php"
+         colors="true"
+         failOnRisky="true"
+         failOnWarning="true"
+         cacheDirectory=".phpunit.cache">
+    <testsuites>
+        <testsuite name="Test Suite">
+            <directory>tests</directory>
+            <exclude>tests/Fixtures</exclude>
+        </testsuite>
+    </testsuites>
+    <source>
+        <include>
+            <directory>bin</directory>
+        </include>
+    </source>
+</phpunit>
diff --git a/tests/AlwaysPassingTest.php b/tests/AlwaysPassingTest.php
new file mode 100644
index 0000000..8251285
--- /dev/null
+++ b/tests/AlwaysPassingTest.php
@@ -0,0 +1,26 @@
+<?php
+
+namespace Tests;
+
+use PHPUnit\Framework\TestCase;
+use Tests\Fixtures\AlwaysPassingFixture;
+
+class AlwaysPassingTest extends TestCase
+{
+    public function test_always_passing_fixture_returns_true(): void
+    {
+        $fixture = new AlwaysPassingFixture();
+        
+        $this->assertTrue(
+            $fixture->success(),
+            'AlwaysPassingFixture should always return true'
+        );
+    }
+    
+    public function test_another_always_passing_test(): void
+    {
+        $fixture = new AlwaysPassingFixture();
+        
+        $this->assertTrue($fixture->success());
+    }
+}
diff --git a/tests/AnotherFailingTest.php b/tests/AnotherFailingTest.php
new file mode 100644
index 0000000..3404e85
--- /dev/null
+++ b/tests/AnotherFailingTest.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace Tests;
+
+use PHPUnit\Framework\TestCase;
+use Tests\Fixtures\AnotherFailingFixture;
+
+class AnotherFailingTest extends TestCase
+{
+    public function test_another_failing_fixture(): void
+    {
+        $fixture = new AnotherFailingFixture();
+        
+        $this->assertTrue(
+            $fixture->success(),
+            'This test will also fail initially'
+        );
+    }
+}
diff --git a/tests/Fixtures/AlwaysPassingFixture.php b/tests/Fixtures/AlwaysPassingFixture.php
new file mode 100644
index 0000000..f24b4c3
--- /dev/null
+++ b/tests/Fixtures/AlwaysPassingFixture.php
@@ -0,0 +1,14 @@
+<?php
+
+namespace Tests\Fixtures;
+
+/**
+ * Fixture class that always passes
+ */
+class AlwaysPassingFixture
+{
+    public function success(): bool
+    {
+        return true;
+    }
+}
diff --git a/tests/Fixtures/AnotherFailingFixture.php b/tests/Fixtures/AnotherFailingFixture.php
new file mode 100644
index 0000000..a642fa2
--- /dev/null
+++ b/tests/Fixtures/AnotherFailingFixture.php
@@ -0,0 +1,16 @@
+<?php
+
+namespace Tests\Fixtures;
+
+/**
+ * Another fixture class that initially fails
+ * Change the return value from false to true to simulate fixing the test
+ */
+class AnotherFailingFixture
+{
+    public function success(): bool
+    {
+        // CHANGEME: false = failing test, true = passing test
+        return true;
+    }
+}
diff --git a/tests/Fixtures/InitiallyFailingFixture.php b/tests/Fixtures/InitiallyFailingFixture.php
new file mode 100644
index 0000000..e8218b1
--- /dev/null
+++ b/tests/Fixtures/InitiallyFailingFixture.php
@@ -0,0 +1,16 @@
+<?php
+
+namespace Tests\Fixtures;
+
+/**
+ * Fixture class that initially fails but can be "fixed"
+ * Change the return value from false to true to simulate fixing the test
+ */
+class InitiallyFailingFixture
+{
+    public function success(): bool
+    {
+        // CHANGEME: false = failing test, true = passing test
+        return true;
+    }
+}
diff --git a/tests/InitiallyFailingTest.php b/tests/InitiallyFailingTest.php
new file mode 100644
index 0000000..dfb4620
--- /dev/null
+++ b/tests/InitiallyFailingTest.php
@@ -0,0 +1,29 @@
+<?php
+
+namespace Tests;
+
+use PHPUnit\Framework\TestCase;
+use Tests\Fixtures\InitiallyFailingFixture;
+
+class InitiallyFailingTest extends TestCase
+{
+    public function test_initially_failing_fixture(): void
+    {
+        $fixture = new InitiallyFailingFixture();
+        
+        $this->assertTrue(
+            $fixture->success(),
+            'This test will fail initially but pass after the fixture is fixed'
+        );
+    }
+    
+    public function test_another_initially_failing_test(): void
+    {
+        $fixture = new InitiallyFailingFixture();
+        
+        $this->assertTrue(
+            $fixture->success(),
+            'Another test that depends on the same fixture'
+        );
+    }
+}
diff --git a/tests/Integration/ScriptBehaviorTest.php b/tests/Integration/ScriptBehaviorTest.php
new file mode 100644
index 0000000..80c8631
--- /dev/null
+++ b/tests/Integration/ScriptBehaviorTest.php
@@ -0,0 +1,293 @@
+<?php
+
+namespace Tests\Integration;
+
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Integration tests that actually execute the bin/phpunit-failed-runner script
+ * These tests verify the script's end-to-end behavior by running it as a subprocess
+ * 
+ * @group integration
+ */
+class ScriptBehaviorTest extends TestCase
+{
+    private string $projectRoot;
+    private string $junitPath;
+    private string $scriptPath;
+    private string $fixtureFilePath;
+    private ?string $originalFixtureContent = null;
+    
+    protected function setUp(): void
+    {
+        $this->projectRoot = dirname(__DIR__, 2);
+        $this->junitPath = $this->projectRoot . '/junit.xml';
+        $this->scriptPath = $this->projectRoot . '/bin/phpunit-failed-runner';
+        $this->fixtureFilePath = $this->projectRoot . '/tests/Fixtures/InitiallyFailingFixture.php';
+        
+        // Clean up any existing junit.xml before each test
+        if (file_exists($this->junitPath)) {
+            unlink($this->junitPath);
+        }
+        
+        // Backup the fixture file
+        $this->originalFixtureContent = file_get_contents($this->fixtureFilePath);
+    }
+    
+    protected function tearDown(): void
+    {
+        // Restore the fixture file
+        if ($this->originalFixtureContent !== null) {
+            file_put_contents($this->fixtureFilePath, $this->originalFixtureContent);
+        }
+        
+        // Clean up junit.xml after each test
+        if (file_exists($this->junitPath)) {
+            unlink($this->junitPath);
+        }
+    }
+    
+    /**
+     * Execute the script and capture output
+     * Uses phpunit-integration-fixtures.xml to only run fixture tests
+     */
+    private function runScript(?string &$output = null): int
+    {
+        $output = [];
+        $exitCode = 0;
+        
+        // Use the fixtures config to only run fixture tests (not the full suite)
+        exec("cd {$this->projectRoot} && {$this->scriptPath} -c phpunit-integration-fixtures.xml 2>&1", $output, $exitCode);
+        $output = implode("\n", $output);
+        
+        return $exitCode;
+    }
+    
+    /**
+     * Make the fixture fail by changing return true to return false
+     */
+    private function makeFixtureFail(): void
+    {
+        $content = file_get_contents($this->fixtureFilePath);
+        $content = str_replace('return true;', 'return false;', $content);
+        file_put_contents($this->fixtureFilePath, $content);
+    }
+    
+    /**
+     * Make the fixture pass by changing return false to return true
+     */
+    private function makeFixturePass(): void
+    {
+        $content = file_get_contents($this->fixtureFilePath);
+        $content = str_replace('return false;', 'return true;', $content);
+        file_put_contents($this->fixtureFilePath, $content);
+    }
+    
+    public function test_script_runs_full_suite_when_no_logfile_exists(): void
+    {
+        // Arrange: No junit.xml exists, make fixture fail so junit.xml persists
+        $this->assertFileDoesNotExist($this->junitPath);
+        $this->makeFixtureFail();
+        
+        // Act: Run the script
+        $exitCode = $this->runScript($output);
+        
+        // Assert: Should run full suite
+        $this->assertEquals(0, $exitCode, 'Script should exit successfully');
+        $this->assertStringContainsString('Logfile not found', $output);
+        $this->assertStringContainsString('Running the test suite', $output);
+        
+        // junit.xml should be created and persist (because test failed)
+        $this->assertFileExists($this->junitPath);
+    }
+    
+    public function test_script_removes_logfile_when_all_tests_pass(): void
+    {
+        // Arrange: Make fixture fail first, run script to create junit.xml
+        $this->makeFixtureFail();
+        $this->runScript($firstOutput);
+        $this->assertFileExists($this->junitPath, 'junit.xml should exist after failed run');
+        
+        // Now fix the fixture
+        $this->makeFixturePass();
+        
+        // Act: Run script again (it should find the logfile with no failures)
+        $exitCode = $this->runScript($output);
+        
+        // Assert: Should clean up the logfile
+        $this->assertEquals(0, $exitCode);
+        $this->assertStringContainsString('Logfile found', $output);
+        $this->assertStringContainsString('No failed tests', $output);
+        $this->assertStringContainsString('Great job', $output);
+        
+        // junit.xml should be removed
+        $this->assertFileDoesNotExist($this->junitPath);
+    }
+    
+    public function test_script_filters_and_reruns_only_failing_tests(): void
+    {
+        // Arrange: Make fixture fail, run script to create junit.xml with failures
+        $this->makeFixtureFail();
+        $this->runScript($firstOutput);
+        
+        $this->assertFileExists($this->junitPath);
+        $this->assertStringContainsString('Logfile not found', $firstOutput);
+        
+        // Act: Run script again (should detect failures and rerun only those tests)
+        $exitCode = $this->runScript($secondOutput);
+        
+        // Assert: Should find and filter failed tests
+        $this->assertEquals(0, $exitCode);
+        $this->assertStringContainsString('Logfile found', $secondOutput);
+        $this->assertStringContainsString('Searching for previously failing tests', $secondOutput);
+        $this->assertStringContainsString('previously failing tests, filtering', $secondOutput);
+        
+        // junit.xml should still exist (tests still failing)
+        $this->assertFileExists($this->junitPath);
+    }
+    
+    public function test_full_workflow_fail_then_fix_then_cleanup(): void
+    {
+        // Phase 1: Run with failing test
+        $this->makeFixtureFail();
+        $exitCode1 = $this->runScript($output1);
+        
+        $this->assertEquals(0, $exitCode1, 'Script should exit successfully even with failures');
+        $this->assertStringContainsString('Logfile not found', $output1);
+        $this->assertFileExists($this->junitPath);
+        
+        // Phase 2: Run again (should detect and rerun failures)
+        $exitCode2 = $this->runScript($output2);
+        
+        $this->assertEquals(0, $exitCode2);
+        $this->assertStringContainsString('Logfile found', $output2);
+        $this->assertStringContainsString('previously failing tests', $output2);
+        $this->assertFileExists($this->junitPath);
+        
+        // Phase 3: Fix the test and run again
+        $this->makeFixturePass();
+        $exitCode3 = $this->runScript($output3);
+        
+        // Assert: After fixing, should clean up
+        $this->assertEquals(0, $exitCode3);
+        $this->assertStringContainsString('Logfile found', $output3);
+        $this->assertStringContainsString('No failed tests', $output3);
+        $this->assertFileDoesNotExist($this->junitPath, 'junit.xml should be cleaned up after all tests pass');
+    }
+    
+    public function test_script_counts_failed_tests_correctly(): void
+    {
+        // Arrange: Make fixture fail
+        $this->makeFixtureFail();
+        $this->runScript();
+        
+        // Act: Run again and check the count in output
+        $this->runScript($output);
+        
+        // Assert: Output should mention the count of failed tests
+        $this->assertStringContainsString('Logfile found', $output);
+        
+        // The script should report finding failed tests
+        $this->assertMatchesRegularExpression(
+            '/Found \d+ previously failing tests/',
+            $output,
+            'Should report count of failed tests'
+        );
+    }
+    
+    public function test_script_exits_with_zero_on_success(): void
+    {
+        // Arrange: All tests passing
+        $this->makeFixturePass();
+        
+        // Act: Run script
+        $exitCode = $this->runScript();
+        
+        // Assert: Should exit with 0
+        $this->assertEquals(0, $exitCode, 'Script should always exit with code 0');
+    }
+    
+    public function test_script_creates_valid_junit_xml(): void
+    {
+        // Arrange: Make fixture fail so junit.xml persists
+        $this->makeFixtureFail();
+        
+        // Act: Run script
+        $this->runScript();
+        
+        // Assert: junit.xml should be valid XML
+        $this->assertFileExists($this->junitPath);
+        
+        $xml = @simplexml_load_file($this->junitPath);
+        $this->assertNotFalse($xml, 'junit.xml should be valid XML');
+        $this->assertEquals('testsuites', $xml->getName());
+    }
+    
+    public function test_script_handles_no_failures_on_first_run(): void
+    {
+        // Arrange: All tests passing
+        $this->makeFixturePass();
+        
+        // Act: Run script (first run, no logfile)
+        $exitCode = $this->runScript($output);
+        
+        // Assert: Should run full suite and clean up immediately if all pass
+        $this->assertEquals(0, $exitCode);
+        $this->assertStringContainsString('Logfile not found', $output);
+        
+        // The logfile might be cleaned up immediately after first run if all tests pass
+        // Check if we see success message
+        if (!file_exists($this->junitPath)) {
+            $this->assertStringContainsString('No failed tests', $output);
+        }
+    }
+    
+    public function test_script_output_contains_expected_messages(): void
+    {
+        // Test that the script outputs the expected emoji/messages
+        $this->makeFixtureFail();
+        $this->runScript($firstOutput);
+        
+        // First run: should see "Logfile not found"
+        $this->assertStringContainsString('Logfile not found', $firstOutput);
+        $this->assertStringContainsString('Running the test suite', $firstOutput);
+        
+        // Second run: should see "Logfile found"
+        $this->runScript($secondOutput);
+        $this->assertStringContainsString('Logfile found', $secondOutput);
+        $this->assertStringContainsString('Searching for previously failing tests', $secondOutput);
+    }
+    
+    public function test_script_persists_junit_xml_when_tests_fail(): void
+    {
+        // Arrange: Make fixture fail
+        $this->makeFixtureFail();
+        
+        // Act: Run script
+        $this->runScript();
+        
+        // Assert: junit.xml should persist (not be deleted)
+        $this->assertFileExists($this->junitPath, 'junit.xml should not be deleted when tests fail');
+    }
+    
+    public function test_script_uses_xmlstarlet_for_transformations(): void
+    {
+        // This test verifies xmlstarlet is available (required dependency)
+        // Act: Run script
+        $exitCode = $this->runScript($output);
+        
+        // Assert: Should not contain errors about xmlstarlet
+        $this->assertStringNotContainsString('xmlstarlet: command not found', $output);
+        $this->assertStringNotContainsString('xmlstarlet: not found', $output);
+    }
+    
+    public function test_script_detects_xsl_files_in_project_root(): void
+    {
+        // Act: Run script
+        $exitCode = $this->runScript($output);
+        
+        // Assert: Should not contain XSL path detection errors
+        $this->assertStringNotContainsString('Cannot find XSL transformation files', $output);
+        $this->assertEquals(0, $exitCode);
+    }
+}
diff --git a/tests/Unit/XslTransformationTest.php b/tests/Unit/XslTransformationTest.php
new file mode 100644
index 0000000..bfb5da9
--- /dev/null
+++ b/tests/Unit/XslTransformationTest.php
@@ -0,0 +1,195 @@
+<?php
+
+namespace Tests\Unit;
+
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Unit tests for XSL transformations
+ * These tests verify the XSL files work correctly with various junit.xml formats
+ */
+class XslTransformationTest extends TestCase
+{
+    private string $projectRoot;
+    
+    protected function setUp(): void
+    {
+        $this->projectRoot = dirname(__DIR__, 1);
+    }
+    
+    public function test_prune_xsl_extracts_failed_tests_from_junit_xml(): void
+    {
+        $junitXml = <<<XML
+<?xml version="1.0" encoding="UTF-8"?>
+<testsuites>
+  <testsuite name="Test Suite" tests="3" assertions="3" errors="0" failures="2" skipped="0" time="0.001">
+    <testcase name="test_passing" class="Tests\PassingTest" assertions="1" time="0.000">
+    </testcase>
+    <testcase name="test_failing_one" class="Tests\FailingTest" assertions="1" time="0.000">
+      <failure type="PHPUnit\Framework\ExpectationFailedException">Failed</failure>
+    </testcase>
+    <testcase name="test_failing_two" class="Tests\AnotherTest" assertions="1" time="0.000">
+      <failure type="PHPUnit\Framework\ExpectationFailedException">Failed</failure>
+    </testcase>
+  </testsuite>
+</testsuites>
+XML;
+
+        $tempFile = tempnam(sys_get_temp_dir(), 'junit');
+        file_put_contents($tempFile, $junitXml);
+        
+        $output = shell_exec("xmlstarlet tr {$this->projectRoot}/../prune.xsl {$tempFile}");
+        
+        $this->assertStringContainsString('<tests>', $output);
+        $this->assertStringContainsString('<test>Tests\FailingTest::test_failing_one</test>', $output);
+        $this->assertStringContainsString('<test>Tests\AnotherTest::test_failing_two</test>', $output);
+        $this->assertStringNotContainsString('PassingTest', $output);
+        
+        unlink($tempFile);
+    }
+    
+    public function test_prune_xsl_handles_errors_as_failures(): void
+    {
+        $junitXml = <<<XML
+<?xml version="1.0" encoding="UTF-8"?>
+<testsuites>
+  <testsuite name="Test Suite" tests="2" assertions="2" errors="1" failures="1" skipped="0" time="0.001">
+    <testcase name="test_with_error" class="Tests\ErrorTest" assertions="1" time="0.000">
+      <error type="Exception">Error occurred</error>
+    </testcase>
+    <testcase name="test_with_failure" class="Tests\FailureTest" assertions="1" time="0.000">
+      <failure type="PHPUnit\Framework\ExpectationFailedException">Failed</failure>
+    </testcase>
+  </testsuite>
+</testsuites>
+XML;
+
+        $tempFile = tempnam(sys_get_temp_dir(), 'junit');
+        file_put_contents($tempFile, $junitXml);
+        
+        $output = shell_exec("xmlstarlet tr {$this->projectRoot}/../prune.xsl {$tempFile}");
+        
+        $this->assertStringContainsString('ErrorTest::test_with_error', $output);
+        $this->assertStringContainsString('FailureTest::test_with_failure', $output);
+        
+        unlink($tempFile);
+    }
+    
+    public function test_count_failed_xsl_counts_tests_correctly(): void
+    {
+        $prunedXml = <<<XML
+<?xml version="1.0"?>
+<tests>
+  <test>Tests\FailingTest::test_one</test>
+  <test>Tests\FailingTest::test_two</test>
+  <test>Tests\AnotherTest::test_three</test>
+</tests>
+XML;
+
+        $tempFile = tempnam(sys_get_temp_dir(), 'pruned');
+        file_put_contents($tempFile, $prunedXml);
+        
+        $count = trim(shell_exec("xmlstarlet tr --omit-decl {$this->projectRoot}/../count-failed.xsl {$tempFile}"));
+        
+        $this->assertEquals('3', $count);
+        
+        unlink($tempFile);
+    }
+    
+    public function test_count_failed_xsl_returns_zero_for_no_failures(): void
+    {
+        $prunedXml = <<<XML
+<?xml version="1.0"?>
+<tests>
+</tests>
+XML;
+
+        $tempFile = tempnam(sys_get_temp_dir(), 'pruned');
+        file_put_contents($tempFile, $prunedXml);
+        
+        $count = trim(shell_exec("xmlstarlet tr --omit-decl {$this->projectRoot}/../count-failed.xsl {$tempFile}"));
+        
+        $this->assertEquals('0', $count);
+        
+        unlink($tempFile);
+    }
+    
+    public function test_failed_tests_xsl_creates_phpunit_filter(): void
+    {
+        $prunedXml = <<<XML
+<?xml version="1.0"?>
+<tests>
+  <test>Tests\FailingTest::test_one</test>
+  <test>Tests\FailingTest::test_two</test>
+  <test>Tests\AnotherTest::test_three</test>
+</tests>
+XML;
+
+        $tempFile = tempnam(sys_get_temp_dir(), 'pruned');
+        file_put_contents($tempFile, $prunedXml);
+        
+        $filter = trim(shell_exec("xmlstarlet tr --omit-decl {$this->projectRoot}/../failed-tests.xsl {$tempFile}"));
+        
+        $this->assertStringContainsString('Tests\\\\FailingTest::test_one', $filter);
+        $this->assertStringContainsString('Tests\\\\FailingTest::test_two', $filter);
+        $this->assertStringContainsString('Tests\\\\AnotherTest::test_three', $filter);
+        $this->assertStringContainsString('|', $filter); // Tests are separated by |
+        
+        unlink($tempFile);
+    }
+    
+    public function test_failed_tests_xsl_escapes_backslashes(): void
+    {
+        $prunedXml = <<<XML
+<?xml version="1.0"?>
+<tests>
+  <test>Tests\Namespace\ClassName::testMethod</test>
+</tests>
+XML;
+
+        $tempFile = tempnam(sys_get_temp_dir(), 'pruned');
+        file_put_contents($tempFile, $prunedXml);
+        
+        $filter = trim(shell_exec("xmlstarlet tr --omit-decl {$this->projectRoot}/../failed-tests.xsl {$tempFile}"));
+        
+        // Backslashes should be escaped for PHPUnit filter
+        $this->assertStringContainsString('Tests\\\\Namespace\\\\ClassName::testMethod', $filter);
+        
+        unlink($tempFile);
+    }
+    
+    public function test_full_transformation_pipeline(): void
+    {
+        $junitXml = <<<XML
+<?xml version="1.0" encoding="UTF-8"?>
+<testsuites>
+  <testsuite name="Test Suite" tests="5" assertions="5" errors="0" failures="2" skipped="0" time="0.001">
+    <testcase name="test_pass_1" class="Tests\PassingTest" assertions="1" time="0.000"></testcase>
+    <testcase name="test_pass_2" class="Tests\PassingTest" assertions="1" time="0.000"></testcase>
+    <testcase name="test_fail_1" class="Tests\FailingTest" assertions="1" time="0.000">
+      <failure type="PHPUnit\Framework\ExpectationFailedException">Failed</failure>
+    </testcase>
+    <testcase name="test_pass_3" class="Tests\PassingTest" assertions="1" time="0.000"></testcase>
+    <testcase name="test_fail_2" class="Tests\FailingTest" assertions="1" time="0.000">
+      <failure type="PHPUnit\Framework\ExpectationFailedException">Failed</failure>
+    </testcase>
+  </testsuite>
+</testsuites>
+XML;
+
+        $tempFile = tempnam(sys_get_temp_dir(), 'junit');
+        file_put_contents($tempFile, $junitXml);
+        
+        // Run full pipeline: prune -> count
+        $count = trim(shell_exec("xmlstarlet tr {$this->projectRoot}/../prune.xsl {$tempFile} | xmlstarlet tr --omit-decl {$this->projectRoot}/../count-failed.xsl"));
+        $this->assertEquals('2', $count);
+        
+        // Run full pipeline: prune -> failed-tests
+        $filter = trim(shell_exec("xmlstarlet tr {$this->projectRoot}/../prune.xsl {$tempFile} | xmlstarlet tr --omit-decl {$this->projectRoot}/../failed-tests.xsl"));
+        $this->assertStringContainsString('Tests\\\\FailingTest::test_fail_1', $filter);
+        $this->assertStringContainsString('Tests\\\\FailingTest::test_fail_2', $filter);
+        $this->assertStringContainsString('|', $filter);
+        
+        unlink($tempFile);
+    }
+}