NUnit2042

Comparison constraint on object

Topic	Value
Id	NUnit2042
Severity	Info
Enabled	True
Category	Assertion
Code	ComparableTypesAnalyzer

Description

The comparison constraint might fail as the actual and the expected value might not implement IComparable.

Motivation

public static void ShouldBeGreaterThan(this object actual, object expected, string? message = null)
{
    Assert.That(actual, Is.GreaterThan(expected), message);
}

In the above function it is assumed that every instance of object is comparable. The function works if the types actually are comparable, but will result in NUnit runtime errors if they are not.

How to fix violations

Change the type to IComparable. This way you will get compilation failures if called with types that do not implement IComparable. A similar solution can be created which works for types implementing the generic IComparable<T>.

public static void ShouldBeGreaterThan(this IComparable actual, IComparable expected, string? message = null)
{
    Assert.That(actual, Is.GreaterThan(expected), message);
}

public static void ShouldBeGreaterThan<T>(this T actual, T expected, string? message = null)
    where T : IComparable<T>
{
    Assert.That(actual, Is.GreaterThan(expected), message);
}

Configure severity

Via ruleset file

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

Via .editorconfig file

# NUnit2042: Comparison constraint on object
dotnet_diagnostic.NUnit2042.severity = chosenSeverity

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

Via #pragma directive

#pragma warning disable NUnit2042 // Comparison constraint on object
Code violating the rule here
#pragma warning restore NUnit2042 // Comparison constraint on object

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

#pragma warning disable NUnit2042 // Comparison constraint on object

Via attribute [SuppressMessage]

[System.Diagnostics.CodeAnalysis.SuppressMessage("Assertion",
    "NUnit2042:Comparison constraint on object",
    Justification = "Reason...")]