Add prose test 4 and drop RequiresPhpExtension from backpressure tests

- Add Prose4: test that maxAdaptiveRetries=1 limits retries to 2 total attempts
- Remove #[RequiresPhpExtension('mongodb', '>= 2.3.0dev')] from all three
  backpressure prose tests since ext-mongodb ^2.3 is now required in composer.json

Author: GromNaN

tests/SpecTests/ClientBackpressure/Prose1_OpRetryExponentialBackoffTest.php

@@ -7,17 +7,15 @@
 use MongoDB\Operation\WithTransaction;
 use MongoDB\Tests\SpecTests\FunctionalTestCase;
 use MongoDB\Tests\UnifiedSpecTests\Util;
-use PHPUnit\Framework\Attributes\RequiresPhpExtension;
 
 use function abs;
 use function hrtime;
 
 /**
  * Prose test 1: Retry operation uses exponential backoff
  *
- * @see https://github.com/mongodb/specifications/blob/master/source/client-backpressure/tests/README.md
+ * @see https://github.com/mongodb/specifications/blob/master/source/client-backpressure/tests/README.md#test-1-operation-retry-uses-exponential-backoff
  */
-#[RequiresPhpExtension('mongodb', '>= 2.3.0dev')]
 class Prose1_OpRetryExponentialBackoffTest extends FunctionalTestCase
 {
     public function testOperationRetryUsesExponentialBackoff(): void

tests/SpecTests/ClientBackpressure/Prose3_OverloadErrorMaxRetryTest.php

@@ -8,14 +8,12 @@
 use MongoDB\Driver\Monitoring\CommandSubscriber;
 use MongoDB\Driver\Monitoring\CommandSucceededEvent;
 use MongoDB\Tests\SpecTests\FunctionalTestCase;
-use PHPUnit\Framework\Attributes\RequiresPhpExtension;
 
 /**
  * Prose test 3: Overload Errors are Retried a Maximum of MAX_RETRIES times
  *
- * @see https://github.com/mongodb/specifications/blob/master/source/client-backpressure/tests/README.md
+ * @see https://github.com/mongodb/specifications/blob/master/source/client-backpressure/tests/README.md#test-3-overload-errors-are-retried-a-maximum-of-max_retries-times
  */
-#[RequiresPhpExtension('mongodb', '>= 2.3.0dev')]
 class Prose3_OverloadErrorMaxRetryTest extends FunctionalTestCase
 {
     private const MAX_RETRIES = 2;

tests/SpecTests/ClientBackpressure/Prose4_OverloadErrorMaxAdaptiveRetriesTest.php

@@ -0,0 +1,71 @@
+<?php
+
+namespace MongoDB\Tests\SpecTests\ClientBackpressure;
+
+use MongoDB\Driver\Exception\RuntimeException;
+use MongoDB\Driver\Monitoring\CommandFailedEvent;
+use MongoDB\Driver\Monitoring\CommandStartedEvent;
+use MongoDB\Driver\Monitoring\CommandSubscriber;
+use MongoDB\Driver\Monitoring\CommandSucceededEvent;
+use MongoDB\Tests\SpecTests\FunctionalTestCase;
+
+/**
+ * Prose test 4: Overload Errors are Retried a Maximum of maxAdaptiveRetries times when configured
+ *
+ * @see https://github.com/mongodb/specifications/blob/master/source/client-backpressure/tests/README.md#test-4-overload-errors-are-retried-a-maximum-of-maxadaptiveretries-times-when-configured
+ */
+class Prose4_OverloadErrorMaxAdaptiveRetriesTest extends FunctionalTestCase
+{
+    private const MAX_ADAPTIVE_RETRIES = 1;
+
+    public function testOverloadErrorsAreRetriedMaxAdaptiveRetryTimes(): void
+    {
+        $this->skipIfServerVersion('<', '4.3.1', 'Test requires configureFailPoint to support errorLabels');
+
+        $client = self::createTestClient(options: ['maxAdaptiveRetries' => self::MAX_ADAPTIVE_RETRIES]);
+        $collection = $client->selectCollection($this->getDatabaseName(), $this->getCollectionName());
+
+        $subscriber = new class implements CommandSubscriber {
+            public int $findCommandsStarted = 0;
+
+            public function commandStarted(CommandStartedEvent $event): void
+            {
+                if ($event->getCommandName() === 'find') {
+                    $this->findCommandsStarted++;
+                }
+            }
+
+            public function commandSucceeded(CommandSucceededEvent $event): void
+            {
+            }
+
+            public function commandFailed(CommandFailedEvent $event): void
+            {
+            }
+        };
+
+        $client->addSubscriber($subscriber);
+
+        $this->configureFailPoint([
+            'configureFailPoint' => 'failCommand',
+            'mode' => 'alwaysOn',
+            'data' => [
+                'failCommands' => ['find'],
+                'errorCode' => 462, // IngressRequestRateLimitExceeded
+                'errorLabels' => ['SystemOverloadedError', 'RetryableError'],
+            ],
+        ]);
+
+        try {
+            $collection->find([]);
+            $this->fail('Expected RuntimeException was not thrown');
+        } catch (RuntimeException $e) {
+            $this->assertTrue($e->hasErrorLabel('RetryableError'));
+            $this->assertTrue($e->hasErrorLabel('SystemOverloadedError'));
+        }
+
+        $client->removeSubscriber($subscriber);
+
+        $this->assertSame(self::MAX_ADAPTIVE_RETRIES + 1, $subscriber->findCommandsStarted);
+    }
+}