Drop support for PHPUnit < 7.5 [6]

Even though the TestListener implementation is not (yet) compatible with PHPUnit 10 (nor 11 or 12), we should still drop support for PHPUnit < 7.5 from the existing implementation.

This includes:
* Dropping support for the PHPUnit 6 specific implementation of the TestListener.
* Removing the semi-duplicate test fixture classes for PHPUnit < 7, as well as removing the test helper method containing the toggle for which fixture to use.
* Updating the documentation in the README.

README.md

@@ -554,11 +554,11 @@ class MyTest extends XTestCase {
 
 > :warning: **Important** :warning:
 >
-> The TestListener polyfill in PHPUnit Polyfills 2.0/3.0 is [not (yet) compatible with PHPUnit 10.x/11.x][polyfill-ticket].
+> The TestListener polyfill in PHPUnit Polyfills 2.0/3.0/4.0 is [not (yet) compatible with PHPUnit 10.x/11.x/12.x][polyfill-ticket].
 >
 > If you need the TestListener polyfill, it is recommended to stay on the PHPUnit Polyfills 1.x series for the time being and to watch and upvote the [related ticket][polyfill-ticket].
 >
-> The below documentation is for the PHPUnit 6.x-9.x TestListener polyfill implementation.
+> The below documentation is for the PHPUnit 7.x-9.x TestListener polyfill implementation.
 
 [polyfill-ticket]: https://github.com/Yoast/PHPUnit-Polyfills/issues/128
 
@@ -567,9 +567,7 @@ Additionally, the use of the TestListener principle has been deprecated in PHPUn
 
 > Note: while deprecated in PHPUnit 7, the TestListener interface has not yet been removed and is still supported in PHPUnit 9.x.
 
-If your test suite does not need to support PHPUnit < 7, it is strongly recommended to use the TestRunner hook interfaces extensions instead.
-
-However, for test suites that still need to support PHPUnit 6 or lower, implementing the `TestListener` interface is the only viable option.
+It is recommended to use the TestRunner hook interfaces extensions instead.
 
 #### `Yoast\PHPUnitPolyfills\TestListeners\TestListenerDefaultImplementation`
 
@@ -592,10 +590,6 @@ Similar to the `TestCase` implementation, snake_case methods without type declar
 
 Implementations of the `TestListener` interface may be using any of the following patterns:
 ```php
-// PHPUnit 6.
-class MyTestListener extends \PHPUnit\Framework\BaseTestListener {}
-
-// PHPUnit 7+.
 class MyTestListener implements \PHPUnit\Framework\TestListener {
     use \PHPUnit\Framework\TestListenerDefaultImplementation;
 }

phpstan.neon.dist

@@ -46,7 +46,7 @@ parameters:
 		# The traits are functionality, but not used by the package itself. Can't be helped.
 		-
 			identifier: trait.unused
-			path: src/TestListeners/TestListenerDefaultImplementationPHPUnit6.php
+			path: src/TestListeners/TestListenerDefaultImplementationPHPUnitGte7.php
 		-
 			identifier: trait.unused
 			path: src/TestListeners/TestListenerSnakeCaseMethods.php

phpunitpolyfills-autoload.php

@@ -361,13 +361,6 @@ public static function loadTestCase() {
 		 * @return void
 		 */
 		public static function loadTestListenerDefaultImplementation() {
-			if ( \version_compare( PHPUnit_Version::id(), '7.0.0', '<' ) ) {
-				// PHPUnit 6.4.4 < 7.0.0.
-				require_once __DIR__ . '/src/TestListeners/TestListenerDefaultImplementationPHPUnit6.php';
-				return;
-			}
-
-			// PHPUnit >= 7.0.0.
 			require_once __DIR__ . '/src/TestListeners/TestListenerDefaultImplementationPHPUnitGte7.php';
 		}
 

tests/TestListeners/Fixtures/Failure.php

@@ -14,7 +14,7 @@ class Failure extends TestCase {
 	 *
 	 * @return void
 	 */
-	protected function runTest() {
+	protected function testForListener() {
 		$this->fail();
 	}
 }

tests/TestListeners/Fixtures/Incomplete.php

@@ -14,7 +14,7 @@ class Incomplete extends TestCase {
 	 *
 	 * @return void
 	 */
-	protected function runTest() {
+	protected function testForListener() {
 		$this->markTestIncomplete( 'Test incomplete' );
 	}
 }

tests/TestListeners/Fixtures/Risky.php

@@ -14,7 +14,7 @@ class Risky extends TestCase {
 	 *
 	 * @return void
 	 */
-	protected function runTest() {
+	protected function testForListener() {
 		$this->markAsRisky();
 	}
 }

tests/TestListeners/Fixtures/Skipped.php

@@ -14,7 +14,7 @@ class Skipped extends TestCase {
 	 *
 	 * @return void
 	 */
-	protected function runTest() {
+	protected function testForListener() {
 		$this->markTestSkipped( 'Skipped test' );
 	}
 }

tests/TestListeners/Fixtures/Success.php

@@ -14,7 +14,7 @@ class Success extends TestCase {
 	 *
 	 * @return void
 	 */
-	protected function runTest() {
+	protected function testForListener() {
 		$this->assertTrue( true );
 	}
 }