DatapointSource

DatapointSourceAttribute is used to mark a field, property, or method as providing a collection of data values for Theory tests. The source must return either an array of the required type or an IEnumerable<T>.

This attribute is ignored for ordinary tests, including parameterized tests using [TestCase].

Usage

This is a parameterless attribute that can be applied to fields, properties, or methods.

[DatapointSource]

Applies To

Field	Property	Parameterless Methods	Test Methods	Test Fixtures (Classes)	Assembly
✅	✅	✅	❌	❌	❌

Note

Parameterless methods used with this attribute must return an array or IEnumerable<T>, and the element type must exactly match the Theory parameter type.

Example

[TestFixture]
public class PrimeNumberTests
{
    // DatapointSource on a field returning an array
    [DatapointSource]
    public int[] SmallPrimes = { 2, 3, 5, 7, 11, 13 };

    // DatapointSource on a property returning IEnumerable<T>
    [DatapointSource]
    public IEnumerable<int> MorePrimes
    {
        get
        {
            yield return 17;
            yield return 19;
            yield return 23;
        }
    }

    // DatapointSource on a method
    [DatapointSource]
    public int[] GetPrimesUnder100()
    {
        return new[] { 29, 31, 37, 41, 43, 47 };
    }

    [Theory]
    public void PrimeIsOddOrTwo(int prime)
    {
        // NUnit combines all datapoint sources for int type
        Assert.That(prime == 2 || prime % 2 != 0);
    }
}

Automatically Supplied Datapoints

NUnit automatically supplies datapoints for certain types:

Type	Automatic Values
`bool`	`true`, `false`
Any `enum`	All defined enum values

If you supply any datapoints for a parameter type, automatic datapoint generation for that type is suppressed.

Notes

The data source must be a member of the class containing the Theory.
The element type must exactly match the parameter type - no implicit conversions are performed.
Multiple DatapointSource attributes of the same type are combined.
Use Datapoint when you only need to provide a single value from a field.
The obsolete DatapointsAttribute was replaced by DatapointSourceAttribute in earlier versions.
The source is evaluated when the tests are loaded, before any setup method runs, and its data must be repeatable. See Load Time and Execution Time.