[9.x] Add assertBadRequest to the TestResponse.

src/Illuminate/Testing/TestResponse.php

@@ -155,6 +155,16 @@ public function assertUnauthorized()
         return $this->assertStatus(401);
     }
 
+    /**
+     * Assert that the response has a bad request status code.
+     *
+     * @return $this
+     */
+    public function assertBadRequest()
+    {
+        return $this->assertStatus(400);
+    }
+
     /**
      * Assert that the response has a 422 status code.
      *

tests/Testing/TestResponseTest.php

@@ -564,6 +564,22 @@ public function testAssertUnauthorized()
         $response->assertUnauthorized();
     }
 
+    public function testAssertBadRequest()
+    {
+        $statusCode = 500;
+
+        $this->expectException(AssertionFailedError::class);
+
+        $this->expectExceptionMessage('Expected response status code');
+
+        $baseResponse = tap(new Response, function ($response) use ($statusCode) {
+            $response->setStatusCode($statusCode);
+        });
+
+        $response = TestResponse::fromBaseResponse($baseResponse);
+        $response->assertBadRequest();
+    }
+
     public function testAssertUnprocessable()
     {
         $statusCode = 500;