NUnit4002

Use Specific constraint

Description

Replace 'EqualTo' with a keyword in the corresponding specific constraint.

Motivation

Sometimes constraints can be written more concisely using the inbuilt constraints provided by NUnit - e.g. Is.True instead of Is.EqualTo(true).

Also, from NUnit version 4.3.0 where new overloads of Is.EqualTo were introduced, it is sometimes not possible to uniquely determine default when provided as the expected value - e.g. in Is.EqualTo(default). Again, in such cases, it is better to use the inbuilt constraint provided by NUnit.

Some examples of constraints that can be be simplified by using a more specific constraint can be seen below.

[Test]
public void Test()
{
    Assert.That(actualFalse, Is.EqualTo(false));
    Assert.That(actualTrue, Is.EqualTo(true));
    Assert.That(actualObject, Is.EqualTo(null));
    Assert.That(actualObject, Is.EqualTo(default));
    Assert.That(actualInt, Is.EqualTo(default));
}

How to fix violations

The analyzer comes with a code fix that will replace the constraint Is.EqualTo(x) with the matching Is.X constraint (for some x). So the code block above will be changed into

[Test]
public void Test()
{
    Assert.That(actualFalse, Is.False);
    Assert.That(actualTrue, Is.True);
    Assert.That(actualObject, Is.Null);
    Assert.That(actualObject, Is.Null);
    Assert.That(actualInt, Is.Default);
}

Configure severity

Via ruleset file

Configure the severity per project, for more info see MSDN.

Via .editorconfig file

# NUnit4002: Use Specific constraint
dotnet_diagnostic.NUnit4002.severity = chosenSeverity

where chosenSeverity can be one of none, silent, suggestion, warning, or error.

Via #pragma directive

#pragma warning disable NUnit4002 // Use Specific constraint
Code violating the rule here
#pragma warning restore NUnit4002 // Use Specific constraint

Or put this at the top of the file to disable all instances.

#pragma warning disable NUnit4002 // Use Specific constraint

Via attribute [SuppressMessage]

[System.Diagnostics.CodeAnalysis.SuppressMessage("Style",
    "NUnit4002:Use Specific constraint",
    Justification = "Reason...")]