Description

If you attempt to do NotMatch(null) on a string it will fail when the string is not null

Complete minimal example reproducing the issue

// Arrange
string testString = "fdgkdfgkjdfg";

// Assert
testString.Should().NotMatch(null);

Expected behavior:

Test should pass as string is not null

Actual behavior:

Test fails

Versions

FluentAssertions 5.10.0
net core 3.1