NUnit1021.md

NUnit1021

The ValueSource should use nameof operator to specify target

Topic	Value
Id	NUnit1021
Severity	Warning
Enabled	True
Category	Structure
Code	ValueSourceUsageAnalyzer

Description

The ValueSource should use nameof operator to specify target.

Motivation

Prevent test rot by ensuring that future renames don't accidentally break tests in an unexpected way. nameof adds some compile-time support in these situations.

How to fix violations

Example Violation

[Test]
public void SampleTest([ValueSource("MyTestSource")] string stringValue)
{
    Assert.That(stringValue.Length, Is.EqualTo(3));
}

public static object[] MyTestSource()
{
    return new object[] {"One", "Two"};
}

Problem

In this case, we're referring to "MyTestSource" as a string directly. This is brittle; should the name of the property change, the test case source would become invalid, and we would not know this until executing tests.

Fix

The fix is to use the C# nameof operator, which produces a string but references the field name. This way, when refactoring and changing the name of your test source, it would also update the name within the nameof() operator.

The fix in action:

[Test]
public void SampleTest([ValueSource(nameof(MyTestSource))] string stringValue)
{
    Assert.That(stringValue.Length, Is.EqualTo(3));
}

public static object[] MyTestSource()
{
    return new object[] {"One", "Two"};
}

Configure severity

Via ruleset file

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

Via .editorconfig file

# NUnit1021: The ValueSource should use nameof operator to specify target
dotnet_diagnostic.NUnit1021.severity = chosenSeverity

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

Via #pragma directive

#pragma warning disable NUnit1021 // The ValueSource should use nameof operator to specify target
Code violating the rule here
#pragma warning restore NUnit1021 // The ValueSource should use nameof operator to specify target

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

#pragma warning disable NUnit1021 // The ValueSource should use nameof operator to specify target

Via attribute [SuppressMessage]

[System.Diagnostics.CodeAnalysis.SuppressMessage("Structure",
    "NUnit1021:The ValueSource should use nameof operator to specify target",
    Justification = "Reason...")]