test: kill LogicalOrAllSubExprNegation mutation in ServerRequest

Add test to kill the LogicalOrAllSubExprNegation mutation on line 158
of ServerRequest::withParsedBody(). The mutation changes the condition
from `is_array($data) || is_object($data)` to `!is_array($data) ||
!is_object($data)`, which would incorrectly enter the params-setting
block for null values.

Also enable failOnWarning in phpunit.xml.dist to ensure PHP warnings
(like foreach on null) fail tests, which is necessary for this mutation
to be detected.

Author: claude

phpunit.xml.dist

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" backupGlobals="false" bootstrap="vendor/autoload.php" colors="true" processIsolation="false" stopOnFailure="false" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/12.5/phpunit.xsd" cacheDirectory=".phpunit.cache" backupStaticProperties="false" failOnWarning="false">
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" backupGlobals="false" bootstrap="vendor/autoload.php" colors="true" processIsolation="false" stopOnFailure="false" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/12.5/phpunit.xsd" cacheDirectory=".phpunit.cache" backupStaticProperties="false" failOnWarning="true">
   <logging>
     <junit outputFile="build/logs/results.xml"/>
   </logging>

tests/src/Unit/Adapter/Psr7/ServerRequestTest.php

@@ -619,4 +619,42 @@ public function testGetQueryParamsWithMultipleParams(): void
         $this->assertEquals('value2', $queryParams['param2']);
         $this->assertEquals('value3', $queryParams['param3']);
     }
+
+    /**
+     * Kill LogicalOrAllSubExprNegation mutation in withParsedBody().
+     *
+     * Original: if (is_array($data) || is_object($data))
+     * Mutant: if (!is_array($data) || !is_object($data))
+     *
+     * For null: original = false||false = false (skips block)
+     *           mutant = true||true = true (enters block, warning on foreach)
+     *
+     * When mutant is applied, foreach(null) triggers E_WARNING which fails the
+     * test due to failOnWarning="true" in phpunit.xml.dist
+     */
+    public function testWithParsedBodyNullKillsLogicalOrAllSubExprNegation(): void
+    {
+        // Start with a request that has existing post params to verify they get cleared
+        $harRequest = (new Request())
+            ->setMethod('POST')
+            ->setUrl(new Uri('https://www.example.com/'))
+            ->setPostData(
+                (new PostData())->setParams([
+                    (new Params())->setName('existing')->setValue('value'),
+                ])
+            );
+
+        $serverRequest = new ServerRequest($harRequest);
+
+        // Verify pre-condition: there are existing params
+        $this->assertTrue($serverRequest->getHarRequest()->getPostData()->hasParams());
+
+        // Call withParsedBody(null) - this must NOT trigger a warning
+        // If mutant is applied: foreach(null as ...) triggers E_WARNING
+        $result = $serverRequest->withParsedBody(null);
+
+        // The null branch should have been taken, clearing the params
+        $this->assertNull($result->getParsedBody());
+        $this->assertFalse($result->getHarRequest()->getPostData()->hasParams());
+    }
 }