[DeadCode] Allow remove createMock method call on RemoveUnusedVariableAssignRector

rules-tests/DeadCode/Rector/Assign/RemoveUnusedVariableAssignRector/Fixture/create_mock_in_test.php.inc

@@ -0,0 +1,30 @@
+<?php
+
+namespace Rector\Tests\DeadCode\Rector\Assign\RemoveUnusedVariableAssignRector\Fixture;
+
+use PHPUnit\Framework\TestCase;
+
+final class CreateMockInTest extends TestCase
+{
+    public function test($params)
+    {
+        $tmp = $this->createMock('SomeClass');
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Tests\DeadCode\Rector\Assign\RemoveUnusedVariableAssignRector\Fixture;
+
+use PHPUnit\Framework\TestCase;
+
+final class CreateMockInTest extends TestCase
+{
+    public function test($params)
+    {
+    }
+}
+
+?>

rules/DeadCode/SideEffect/SideEffectNodeDetector.php

@@ -18,6 +18,8 @@
 use PhpParser\Node\Name;
 use PhpParser\Node\Name\FullyQualified;
 use PHPStan\Type\ObjectType;
+use Rector\NodeNameResolver\NodeNameResolver;
+use Rector\NodeTypeResolver\NodeTypeResolver;
 use Rector\PhpParser\Node\BetterNodeFinder;
 
 final readonly class SideEffectNodeDetector
@@ -35,6 +37,8 @@
     public function __construct(
         private PureFunctionDetector $pureFunctionDetector,
         private BetterNodeFinder $betterNodeFinder,
+        private NodeTypeResolver $nodeTypeResolver,
+        private NodeNameResolver $nodeNameResolver
     ) {
     }
 
@@ -64,6 +68,10 @@ public function detectCallExpr(Node $node): bool
             return false;
         }
 
+        if (($node instanceof MethodCall || $node instanceof StaticCall) && $this->isTestMock($node)) {
+            return false;
+        }
+
         $exprClass = $node::class;
         if (in_array($exprClass, self::CALL_EXPR_SIDE_EFFECT_NODE_TYPES, true)) {
             return true;
@@ -82,6 +90,18 @@ public function detectCallExpr(Node $node): bool
         return false;
     }
 
+    private function isTestMock(MethodCall|StaticCall $node): bool
+    {
+        $objectType = new ObjectType('PHPUnit\Framework\TestCase');
+        $nodeCaller = $node instanceof MethodCall ? $node->var : $node->class;
+
+        if (! $this->nodeTypeResolver->isObjectType($nodeCaller, $objectType)) {
+            return false;
+        }
+
+        return $this->nodeNameResolver->isName($node->name, 'createMock');
+    }
+
     private function isPhpParser(New_ $new): bool
     {
         if (! $new->class instanceof FullyQualified) {