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Posts Tagged ‘FluentAssertions’

Playing with FluentAssertions

Posted by Kash Farooq on February 23, 2012

I thought I’d try a FluentAssertions – a different way of doing asserts in Unit Tests.

As the name of the library suggests, your assertion code is fluent. i.e. methods are chained.

Some examples.

A simple assert:


To check a list has the correct number of elements:


To ensure that a list has elements in a certain order:

IEnumerable<int> positions = personList.Select(x => x.Rank);
positions.Should().ContainInOrder(new[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 10});

There are lots of helper methods and the lots of examples in the on-line documentation.

I quite like it and have been using it on a project.

And it’s not just the assertion style that I like.

The thing that really impressed me was when one of my tests failed. In my assert I was comparing two strings. I clearly should have done a .Trim() on my string under test, but I forgot. And here is the error I saw in my test runner window:

Expected string to be
"John Smith", but it has unexpected whitespace at the end.

How useful is that! No more “the string differs at position 45”.

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