Question

This code works fine

    [Test]
    public void boo()
    {
        var collection = new[] { 1, 2, 3 };
        collection.Should().Equal(1, 2, 3);
    }

But, this fails

    [Test]
    public void foo()
    {
        var collection = new[] { "1", "2", "3" };
        collection.Should().Equal("1", "2", "3");            
    }

The failure message is:

‘Expected collection to be equal to {1} because 2, but {“1”, “2”, “3”}
contains 2 item(s) too many.’

What is wrong here? Why enumerable of string could not be compared?

And, of cause, my question is – how to handle case in foo() ?

Answer 1

This happens because the compiler selects the wrong overload of Equals() because of limitations in C#. In your particular case, it’s taking the Equals(string expected, string reason, params string[] args), instead of Equals(IEnumerable). I have never found an easy way to solve this ambiguity in FluentAssertions.

To solve your problem, wrap the expected values in an array.

[Test] 
public void foo()  
{ 
  var collection = new[] { "1", "2", "3" }; 
  collection.Should().Equal(new[] {"1", "2", "3"});              
}