Http test redirecting to \ instead of login

Hi I am trying out testing in laravel5.6, but when try to test invalid login like below

public function testInvalidLogin()
    {
        $response = $this->post('/login',[ 'email'=>'[email protected]', 'password'=>'secret' ]);
        $response->assertStatus(302);
        $response->assertLocation('/login');
 }

but when i run this i got error

Failed asserting that two strings are equal.
--- Expected
+++ Actual
@@ @@
-'http://localhost/login'
+'http://localhost'

D:\project\larademo\vendor\laravel\framework\src\Illuminate\Foundation\Testing\TestResponse.php:198
D:\project\larademo\tests\Feature\ExampleTest.php:38

FAILURES!
Tests: 3, Assertions: 5, Failures: 1.

I have also use followingRedirects() but it is giving response code 200 and content of '/'

can you help me what is wrong here