[5.7] Improve assertJsonValidationErrors error message, make it fail when no keys given

src/Illuminate/Foundation/Testing/TestResponse.php

@@ -638,13 +638,22 @@ public function assertJsonCount(int $count, $key = null)
      */
     public function assertJsonValidationErrors($keys)
     {
+        $keys = Arr::wrap($keys);
+
+        PHPUnit::assertNotEmpty($keys, 'You need to provide at least one expected key');
+
         $errors = $this->json()['errors'] ?? [];
 
-        foreach (Arr::wrap($keys) as $key) {
+        $errorMessage = $errors
+            ? 'Response has the following JSON validation errors: '.
+            PHP_EOL.PHP_EOL.json_encode($errors, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE)
+            : 'Response does not have JSON validation errors';
+
+        foreach ($keys as $key) {
             PHPUnit::assertArrayHasKey(
                 $key,
                 $errors,
-                "Failed to find a validation error in the response for key: '{$key}'"
+                "Failed to find a validation error in the response for key: '{$key}'".PHP_EOL.PHP_EOL.$errorMessage
             );
         }
 

tests/Foundation/FoundationTestResponseTest.php

@@ -344,6 +344,17 @@ public function testAssertJsonValidationErrorsCanFailWhenThereAreNoErrors()
         $testResponse->assertJsonValidationErrors('bar');
     }
 
+    public function testAssertJsonValidationErrorsFailsWhenGivenAnEmptyArray()
+    {
+        $this->expectException(AssertionFailedError::class);
+
+        $testResponse = TestResponse::fromBaseResponse(
+            (new Response)->setContent(json_encode(['errors' => ['foo' => 'oops']]))
+        );
+
+        $testResponse->assertJsonValidationErrors([]);
+    }
+
     public function testAssertJsonMissingValidationErrors()
     {
         $baseResponse = tap(new Response, function ($response) {