Initial work on triggering PHP's garbage collector after each n-th test

src/Runner/GarbageCollection/GarbageCollectionHandler.php

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+<?php declare(strict_types=1);
+/*
+ * This file is part of PHPUnit.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+namespace PHPUnit\Runner\GarbageCollection;
+
+use function gc_collect_cycles;
+use function gc_disable;
+use function gc_enable;
+use PHPUnit\Event\EventFacadeIsSealedException;
+use PHPUnit\Event\Facade;
+use PHPUnit\Event\UnknownSubscriberTypeException;
+
+/**
+ * @internal This class is not covered by the backward compatibility promise for PHPUnit
+ */
+final class GarbageCollectionHandler
+{
+    private readonly int $threshold;
+    private int $tests = 0;
+
+    /**
+     * @throws EventFacadeIsSealedException
+     * @throws UnknownSubscriberTypeException
+     */
+    public function __construct(Facade $facade, int $threshold)
+    {
+        $this->threshold = $threshold;
+
+        $this->registerSubscribers($facade);
+    }
+
+    public function executionStarted(): void
+    {
+        gc_disable();
+        gc_collect_cycles();
+    }
+
+    public function executionFinished(): void
+    {
+        gc_collect_cycles();
+        gc_enable();
+    }
+
+    public function testFinished(): void
+    {
+        $this->tests++;
+
+        if ($this->tests === $this->threshold) {
+            gc_collect_cycles();
+
+            $this->tests = 0;
+        }
+    }
+
+    /**
+     * @throws EventFacadeIsSealedException
+     * @throws UnknownSubscriberTypeException
+     */
+    private function registerSubscribers(Facade $facade): void
+    {
+        $facade->registerSubscribers(
+            new ExecutionStartedSubscriber($this),
+            new ExecutionFinishedSubscriber($this),
+            new TestFinishedSubscriber($this),
+        );
+    }
+}

src/Runner/GarbageCollection/Subscriber/ExecutionFinishedSubscriber.php

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+<?php declare(strict_types=1);
+/*
+ * This file is part of PHPUnit.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+namespace PHPUnit\Runner\GarbageCollection;
+
+use PHPUnit\Event\InvalidArgumentException;
+use PHPUnit\Event\TestRunner\ExecutionFinished;
+use PHPUnit\Event\TestRunner\ExecutionFinishedSubscriber as TestRunnerExecutionFinishedSubscriber;
+
+/**
+ * @internal This class is not covered by the backward compatibility promise for PHPUnit
+ */
+final class ExecutionFinishedSubscriber extends Subscriber implements TestRunnerExecutionFinishedSubscriber
+{
+    /**
+     * @throws \PHPUnit\Framework\InvalidArgumentException
+     * @throws InvalidArgumentException
+     */
+    public function notify(ExecutionFinished $event): void
+    {
+        $this->handler()->executionFinished();
+    }
+}

src/Runner/GarbageCollection/Subscriber/ExecutionStartedSubscriber.php

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+<?php declare(strict_types=1);
+/*
+ * This file is part of PHPUnit.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+namespace PHPUnit\Runner\GarbageCollection;
+
+use PHPUnit\Event\InvalidArgumentException;
+use PHPUnit\Event\TestRunner\ExecutionStarted;
+use PHPUnit\Event\TestRunner\ExecutionStartedSubscriber as TestRunnerExecutionStartedSubscriber;
+
+/**
+ * @internal This class is not covered by the backward compatibility promise for PHPUnit
+ */
+final class ExecutionStartedSubscriber extends Subscriber implements TestRunnerExecutionStartedSubscriber
+{
+    /**
+     * @throws \PHPUnit\Framework\InvalidArgumentException
+     * @throws InvalidArgumentException
+     */
+    public function notify(ExecutionStarted $event): void
+    {
+        $this->handler()->executionStarted();
+    }
+}

src/Runner/GarbageCollection/Subscriber/Subscriber.php

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+<?php declare(strict_types=1);
+/*
+ * This file is part of PHPUnit.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+namespace PHPUnit\Runner\GarbageCollection;
+
+/**
+ * @internal This class is not covered by the backward compatibility promise for PHPUnit
+ */
+abstract class Subscriber
+{
+    private readonly GarbageCollectionHandler $handler;
+
+    public function __construct(GarbageCollectionHandler $handler)
+    {
+        $this->handler = $handler;
+    }
+
+    protected function handler(): GarbageCollectionHandler
+    {
+        return $this->handler;
+    }
+}

src/Runner/GarbageCollection/Subscriber/TestFinishedSubscriber.php

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+<?php declare(strict_types=1);
+/*
+ * This file is part of PHPUnit.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+namespace PHPUnit\Runner\GarbageCollection;
+
+use PHPUnit\Event\InvalidArgumentException;
+use PHPUnit\Event\Test\Finished;
+use PHPUnit\Event\Test\FinishedSubscriber;
+
+/**
+ * @internal This class is not covered by the backward compatibility promise for PHPUnit
+ */
+final class TestFinishedSubscriber extends Subscriber implements FinishedSubscriber
+{
+    /**
+     * @throws \PHPUnit\Framework\InvalidArgumentException
+     * @throws InvalidArgumentException
+     */
+    public function notify(Finished $event): void
+    {
+        $this->handler()->testFinished();
+    }
+}