v2 v3 AOT   Warning

xUnit2033

"Use the assertion return value instead of re-deriving it"

Cause

A violation of this rule occurs when the developer uses a narrowing or converting assertion (which returns the narrowed or converted value), but does not utilize the return value and instead re-writes the narrowing or conversion.

Reason for rule

The assertion framework will already provide the narrowing or conversion operation for you. It's less efficient to throw the value away and redo the work yourself.

How to fix violations

To fix a violation of this rule, utilize the return value of the assertion.

Examples

Violates

using System.Linq;
using Xunit;

public class xUnit2033
{
    [Fact]
    public void TestMethod()
    {
        var collection = new[] { 1 };

        Assert.Single(collection);
        Assert.Equal(1, collection.Single());
    }
}

using Xunit;

public class xUnit2033
{
    [Theory]
    [InlineData("Hello world")]
    public void TestMethod(object value)
    {
        Assert.IsType<string>(value);
        Assert.StartsWith("Hello", (string)value);
    }
}

Does not violate

using Xunit;

public class xUnit2033
{
    [Fact]
    public void TestMethod()
    {
        var collection = new[] { 1 };

        var value = Assert.Single(collection);
        Assert.Equal(1, value);
    }
}

using Xunit;

public class xUnit2033
{
    [Theory]
    [InlineData("Hello world")]
    public void TestMethod(object value)
    {
        var stringValue = Assert.IsType<string>(value);
        Assert.StartsWith("Hello", stringValue);
    }
}