Add test to show incorrect behaviour

Author: kubawerlos

tests/_files/DuplicateKeyDataProvidersTest.php

@@ -0,0 +1,37 @@
+<?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\TestFixture;
+
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+
+final class DuplicateKeyDataProvidersTest extends TestCase
+{
+    public static function dataProvider1(): iterable
+    {
+        return [
+            'bar' => [1],
+        ];
+    }
+
+    public static function dataProvider2(): iterable
+    {
+        return [
+            'bar' => [2],
+        ];
+    }
+
+    #[DataProvider('dataProvider1')]
+    #[DataProvider('dataProvider2')]
+    public function test($value): void
+    {
+        $this->assertSame(2, $value);
+    }
+}

tests/unit/Metadata/Api/DataProviderTest.php

@@ -14,6 +14,7 @@
 use PHPUnit\Framework\Attributes\Small;
 use PHPUnit\Framework\InvalidDataProviderException;
 use PHPUnit\Framework\TestCase;
+use PHPUnit\TestFixture\DuplicateKeyDataProvidersTest;
 use PHPUnit\TestFixture\DuplicateKeyDataProviderTest;
 use PHPUnit\TestFixture\MultipleDataProviderTest;
 use PHPUnit\TestFixture\VariousIterableDataProviderTest;
@@ -156,12 +157,24 @@ public function testWithVariousIterableNonStaticDataProviders(): void
         ], $dataSets);
     }
 
-    public function testWithDuplicateKeyDataProviders(): void
+    public function testWithDuplicateKeyDataProvider(): void
     {
         $this->expectException(InvalidDataProviderException::class);
         $this->expectExceptionMessage('The key "foo" has already been defined by a previous data provider');
 
         /* @noinspection UnusedFunctionResultInspection */
         (new DataProvider)->providedData(DuplicateKeyDataProviderTest::class, 'test');
     }
+
+    public function testWithDuplicateKeyDataProviders(): void
+    {
+        $dataSets = (new DataProvider)->providedData(DuplicateKeyDataProvidersTest::class, 'test');
+
+        $this->assertSame(
+            [
+                'bar' => [2],
+            ],
+            $dataSets,
+        );
+    }
 }