gistfile1.php

public function test()
{
  $mock = Mockery::mock('Illuminate\Contracts\Auth\Guard');
  app()->instance('Illuminate\Contracts\Auth\Guard', $mock);

  $this->call('POST', 'auth\login', ['email' => 'example@gmail.com', 'password' => 'asasdsdfb']);

  $mock->shouldReceive('attempt')->once()->andReturn('false');
}


//within the AuthenticatesAndRegistersUsers Trait
public function postLogin(Request $request)
	{
		$this->validate($request, [
			'email' => 'required', 'password' => 'required',
		]);

		$credentials = $request->only('email', 'password');

		if ($this->auth->attempt($credentials, $request->has('remember')))
		{
			return redirect()->intended($this->redirectPath());
		}

		return redirect('/auth/login')
					->withInput($request->only('email'))
					->withErrors([
						'email' => 'These credentials do not match our records.',
					]);
	}