Tests: finish off namespacing

Now all test classes are namespaced, the old autoloader in the test bootstrap is no longer necessary.

Additionally, as long as Composer knows about the namespaced test classes. the (new) custom autoloader is only really needed when PHPUnit is run via a PHAR file.

To this end, this commit:
* Adds a `autoload-dev` section to the `composer.json` configuration file.
* Removes the old autoloader.
* And places the "manual" loading of the PHPUnit polyfills autoloader and the custom autoloader in a condition, so they only get used when the tests are run via a PHAR file.

composer.json

@@ -54,6 +54,11 @@
       "Requests": "library/"
     }
   },
+  "autoload-dev": {
+    "psr-4": {
+      "Requests\\Tests\\": "tests/"
+    }
+  },
   "scripts": {
     "lint": [
       "@php ./vendor/php-parallel-lint/php-parallel-lint/parallel-lint . -e php --exclude vendor --exclude .git"

tests/bootstrap.php

@@ -36,44 +36,40 @@ function define_from_env($name, $default = false) {
 	die(1);
 }
 
-// Load the PHPUnit Polyfills autoloader.
-require_once $vendor_dir . '/yoast/phpunit-polyfills/phpunitpolyfills-autoload.php';
+if (defined('__PHPUNIT_PHAR__')) {
+	// Testing via a PHPUnit phar.
 
-// New autoloader.
-spl_autoload_register(
-	function ($class_name) {
-		// Only try & load our own classes.
-		if (stripos($class_name, 'Requests\\Tests\\') !== 0) {
-			return false;
-		}
+	// Load the PHPUnit Polyfills autoloader.
+	require_once $vendor_dir . '/yoast/phpunit-polyfills/phpunitpolyfills-autoload.php';
 
-		// Strip namespace prefix 'Requests\Tests\'.
-		$relative_class = substr($class_name, 15);
-		$file           = realpath(__DIR__ . '/' . strtr($relative_class, '\\', '/') . '.php');
+	/*
+	 * Autoloader specifically for the test files.
+	 * Fixes issues with PHPUnit not being able to find test classes being extended when running
+	 * in a non-Composer context.
+	 */
+	spl_autoload_register(
+		function ($class_name) {
+			// Only try & load our own classes.
+			if (stripos($class_name, 'Requests\\Tests\\') !== 0) {
+				return false;
+			}
 
-		if (file_exists($file)) {
-			include_once $file;
-		}
+			// Strip namespace prefix 'Requests\Tests\'.
+			$relative_class = substr($class_name, 15);
+			$file           = realpath(__DIR__ . '/' . strtr($relative_class, '\\', '/') . '.php');
 
-		return true;
-	}
-);
-
-// Old autoloader.
-function autoload_tests($class) {
-	if (strpos($class, 'RequestsTest_') !== 0) {
-		return;
-	}
+			if (file_exists($file)) {
+				include_once $file;
+			}
 
-	$class = substr($class, 13);
-	$file  = str_replace('_', '/', $class);
-	if (file_exists(__DIR__ . '/' . $file . '.php')) {
-		require_once __DIR__ . '/' . $file . '.php';
-	}
+			return true;
+		}
+	);
+} else {
+	// Testing via a Composer setup.
+	require_once $vendor_dir . '/autoload.php';
 }
 
-spl_autoload_register('autoload_tests');
-
 function httpbin($suffix = '', $ssl = false) {
 	$host = $ssl ? 'https://' . REQUESTS_TEST_HOST_HTTPS : 'http://' . REQUESTS_TEST_HOST_HTTP;
 	return rtrim($host, '/') . '/' . ltrim($suffix, '/');