minor #26002 Improve assertions (carusogabriel)

This PR was merged into the 3.4 branch.

Discussion
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Improve assertions

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Following #25420 in `3.4` branch.

Commits
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829f59d Improve assertions

Author: nicolas-grekas

Tests/DependencyInjection/FrameworkExtensionTest.php

@@ -1123,7 +1123,7 @@ private function assertCachePoolServiceDefinitionIsCreated(ContainerBuilder $con
         $this->assertFalse($poolDefinition->isAbstract(), sprintf('Service definition "%s" is not abstract.', $id));
 
         $tag = $poolDefinition->getTag('cache.pool');
-        $this->assertTrue(isset($tag[0]['default_lifetime']), 'The default lifetime is stored as an attribute of the "cache.pool" tag.');
+        $this->assertArrayHasKey('default_lifetime', $tag[0], 'The default lifetime is stored as an attribute of the "cache.pool" tag.');
         $this->assertSame($defaultLifetime, $tag[0]['default_lifetime'], 'The default lifetime is stored as an attribute of the "cache.pool" tag.');
 
         $parentDefinition = $poolDefinition;