Fix inversion of expected and actual on assertHeader (#19110)

Author: stephane-monnot

src/Illuminate/Foundation/Testing/TestResponse.php

@@ -114,7 +114,7 @@ public function assertHeader($headerName, $value = null)
 
         if (! is_null($value)) {
             PHPUnit::assertEquals(
-                $this->headers->get($headerName), $value,
+                $value, $this->headers->get($headerName),
                 "Header [{$headerName}] was found, but value [{$actual}] does not match [{$value}]."
             );
         }

tests/Foundation/FoundationTestResponseTest.php

@@ -39,6 +39,22 @@ public function testAssertSeeText()
         $response->assertSeeText('foobar');
     }
 
+    public function testAssertHeader()
+    {
+        $baseResponse = tap(new Response, function ($response) {
+            $response->header('Location', '/foo');
+        });
+
+        $response = TestResponse::fromBaseResponse($baseResponse);
+
+        try {
+            $response->assertHeader('Location', '/bar');
+        } catch (\PHPUnit_Framework_ExpectationFailedException $e) {
+            $this->assertEquals('/bar', $e->getComparisonFailure()->getExpected());
+            $this->assertEquals('/foo', $e->getComparisonFailure()->getActual());
+        }
+    }
+
     public function testAssertJsonWithArray()
     {
         $response = TestResponse::fromBaseResponse(new Response(new JsonSerializableSingleResourceStub));