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xUnit2031 v2 v3 Warning

Do not use Where clause with Assert.Single

Cause

A violation of this rule occurs when using a LINQ Where clause to filter items before calling Assert.Single.

Reason for rule

A more concise overload of Assert.Single allows filtering and shows intent better.

How to fix violations

To fix a violation of this rule, use the overload of Assert.Single that takes a filter function.

Examples

Violates

using System.Linq;
using Xunit;

public class xUnit2031
{
    [Fact]
    public void TestMethod()
    {
        int[] collection = [1, 3, 5, 6, 9];

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

Does not violate

using Xunit;

public class xUnit2031
{
    [Fact]
    public void TestMethod()
    {
        int[] collection = [1, 3, 5, 6, 9];

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