Here is a good page object test

GoodTest.cs

[Test]
public void ShouldNotBeAbleToLoginWithLockedOutUser()
{
    _loginPage.Open();
    //Although I would likely never test a login through the UI. This is just a small example
    var productsPage = _loginPage.Login("locked_out_user", "secret_sauce");
    productsPage.IsLoaded.Should().BeFalse("we used a locked out user who should not be able to login.");
}