Wrap errors, and allow no arguments (#38422)

Author: dwightwatson

src/Illuminate/Testing/TestResponse.php

@@ -1073,7 +1073,7 @@ public function assertValid($keys = null, $errorBag = 'default', $responseKey =
      * @param  string  $responseKey
      * @return $this
      */
-    public function assertInvalid($errors,
+    public function assertInvalid($errors = null,
                                   $errorBag = 'default',
                                   $responseKey = 'errors')
     {
@@ -1092,7 +1092,7 @@ public function assertInvalid($errors,
                         PHP_EOL.PHP_EOL.json_encode($sessionErrors, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE).PHP_EOL
                 : 'Response does not have validation errors in the session.';
 
-        foreach ($errors as $key => $value) {
+        foreach (Arr::wrap($errors) as $key => $value) {
             PHPUnit::assertArrayHasKey(
                 (is_int($key)) ? $value : $key,
                 $sessionErrors,

tests/Testing/TestResponseTest.php

@@ -947,7 +947,11 @@ public function testAssertSessionValidationErrorsUsingAssertInvalid()
 
         $testResponse = TestResponse::fromBaseResponse(new Response);
 
+        $testResponse->assertValid('last_name');
         $testResponse->assertValid(['last_name']);
+
+        $testResponse->assertInvalid();
+        $testResponse->assertInvalid('first_name');
         $testResponse->assertInvalid(['first_name']);
         $testResponse->assertInvalid(['first_name' => 'required']);
         $testResponse->assertInvalid(['first_name' => 'character']);