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xUnit2029 Warning

Do not use Assert.Empty to check if a value does not exist in a collection

Cause

This issue is triggered by using a LINQ Where class with Assert.Empty to make sure no matching items exist in a collection.

Reason for rule

Using a LINQ Where clause to filter items from a collection, and then using Assert.Empty to make sure there are no matching items, gives a less useful reporting result than using Assert.DoesNotContain (as well as the updated code better illustrating the intent of the test).

How to fix violations

To fix a violation of this rule, it is recommended that you use Assert.DoesNotContain instead.

Examples

Violates

using System.Linq;
using Xunit;

public class xUnit2029
{
    [Fact]
    public void TestMethod()
    {
        var collection = new[] { 1, 2, 3 };

        Assert.Empty(collection.Where(i => i % 2 == 0));
    }
}

Does not violate

using Xunit;

public class xUnit2029
{
    [Fact]
    public void TestMethod()
    {
        var collection = new[] { 1, 2, 3 };

        Assert.DoesNotContain(collection, i => i % 2 == 0);
    }
}
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