NUnit2047

Incompatible types for Within constraint

Topic	Value
Id	NUnit2047
Severity	Warning
Enabled	True
Category	Assertion
Code	WithinUsageAnalyzer

Description

The Within modifier should only be used for numeric or Date/Time arguments or tuples containing only these element types. Using it on other types will not have any effect.

Motivation

To bring developers' attention to a scenario in which their code is actually having no effect and may reveal that their test is not doing what they expect.

How to fix violations

Example Violation

[Test]
public void RecordsEqualsMismatch()
{
    var a = new Data(1, 1.0);
    var b = new Data(1, 1.1);

    Assert.That(a, Is.EqualTo(b).Within(0.2), $"{a} != {b}");
}

private sealed record Data(int number, double Value);

Explanation

Using Within here doesn't make any sense, because NUnit cannot apply comparison with tolerance to the types we're comparing.

Fix

Remove the errant call to Within:

[Test]
public void RecordsEqualsMismatch()
{
    var a = new Data(1, 1.0);
    var b = new Data(1, 1.1);

    Assert.That(a, Is.EqualTo(b), $"{a} != {b}");
}

private sealed record Data(int number, double Value);

Configure severity

Via ruleset file

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

Via .editorconfig file

# NUnit2047: Incompatible types for Within constraint
dotnet_diagnostic.NUnit2047.severity = chosenSeverity

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

Via #pragma directive

#pragma warning disable NUnit2047 // Incompatible types for Within constraint
Code violating the rule here
#pragma warning restore NUnit2047 // Incompatible types for Within constraint

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

#pragma warning disable NUnit2047 // Incompatible types for Within constraint

Via attribute [SuppressMessage]

[System.Diagnostics.CodeAnalysis.SuppressMessage("Assertion",
    "NUnit2047:Incompatible types for Within constraint",
    Justification = "Reason...")]