NUnit1016

The source type does not have a default constructor

Topic	Value
Id	NUnit1016
Severity	Error
Enabled	True
Category	Structure
Code	TestCaseSourceUsesStringAnalyzer

Description

The source type must have a default constructor in order to provide test cases.

Motivation

To prevent tests that will fail at runtime due to improper construction.

How to fix violations

Example Violation

public class MyTestClass
{
    [TestCaseSource(typeof(DivideCases))]
    public void DivideTest(int n, int d, int q)
    {
        Assert.AreEqual(q, n / d);
    }
}

class DivideCases : IEnumerable
{
    public DivideCases(int i) { }

    public IEnumerator GetEnumerator()
    {
        yield return new object[] { 12, 3, 4 };
        yield return new object[] { 12, 2, 6 };
        yield return new object[] { 12, 4, 3 };
    }
}

Explanation

In the sample above, the class DivideCases does not have a default constructor - i.e. a constructor with no parameters.

However, source types specified by TestCaseSource must have a default constructor.

Fix

Add a default constructor to the source type (or remove the parameters from an existing constructor):

public class MyTestClass
{
    [TestCaseSource(typeof(DivideCases))]
    public void DivideTest(int n, int d, int q)
    {
        Assert.AreEqual(q, n / d);
    }
}

class DivideCases : IEnumerable
{
    public DivideCases() { }

    public DivideCases(int i) { }

    public IEnumerator GetEnumerator()
    {
        yield return new object[] { 12, 3, 4 };
        yield return new object[] { 12, 2, 6 };
        yield return new object[] { 12, 4, 3 };
    }
}

Configure severity

Via ruleset file

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

Via .editorconfig file

# NUnit1016: The source type does not have a default constructor
dotnet_diagnostic.NUnit1016.severity = chosenSeverity

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

Via #pragma directive

#pragma warning disable NUnit1016 // The source type does not have a default constructor
Code violating the rule here
#pragma warning restore NUnit1016 // The source type does not have a default constructor

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

#pragma warning disable NUnit1016 // The source type does not have a default constructor

Via attribute [SuppressMessage]

[System.Diagnostics.CodeAnalysis.SuppressMessage("Structure",
    "NUnit1016:The source type does not have a default constructor",
    Justification = "Reason...")]