Assert.Fail

The Assert.Fail method allows you to immediately end the test, recording it as failed. Use of Assert.Fail allows you to generate failure messages for tests that are not encapsulated by the other Assert methods. It is also useful in developing your own project-specific assertions.

Assert.Fail(string message=null, params object[] args);

Here's an example of its use to create a private assertion that tests whether a string contains an expected value.

public void AssertStringContains(string expected, string actual)
{
    AssertStringContains(expected, actual, string.Empty);
}

public void AssertStringContains(string expected, string actual, string message)
{
    if (actual.IndexOf(expected) < 0)
        Assert.Fail(message);
}