Random

RandomAttribute is used to specify a set of random values to be provided for an individual parameter of a parameterized test method. It supports numeric types, Guid, and enums.

Constructors

Count Only (Auto-detect Type)

RandomAttribute(int count)
Parameter Type Description
count int The number of random values to generate. The type is inferred from the parameter.

With Range (Type-specific)

RandomAttribute(int min, int max, int count)
RandomAttribute(double min, double max, int count)
// Also available for: uint, long, ulong, short, ushort, byte, sbyte, float
Parameter Type Description
min varies The minimum value (inclusive).
max varies The maximum value (exclusive).
count int The number of random values to generate.

Properties

Property Type Description Default
Distinct bool When true, no value will be repeated among the generated values. false

Applies To

Method Parameters Test Methods Test Fixtures (Classes) Assembly
✅ ❌ ❌ ❌

Supported Types

Type Count-only With Range
int, uint, long, ulong Yes Yes
short, ushort, byte, sbyte Yes Yes
double, float Yes Yes
decimal Yes No (use int or double range)
Guid Yes No
enum Yes No

Examples

Basic Usage

[TestFixture]
public class RandomBasicTests
{
    [Test]
    public void TestWithRandomInts([Random(5)] int value)
    {
        // Generates 5 random int values across the full int range
        TestContext.Out.WriteLine($"Testing with value: {value}");
        Assert.That(value, Is.TypeOf<int>());
    }

    [Test]
    public void TestWithRandomDoubles([Random(3)] double value)
    {
        // Generates 3 random doubles between 0.0 and 1.0
        TestContext.Out.WriteLine($"Testing with value: {value}");
        Assert.That(value, Is.InRange(0.0, 1.0));
    }
}

With Range

[TestFixture]
public class RandomRangeTests
{
    [Test]
    public void TestWithIntRange([Random(1, 100, 5)] int value)
    {
        // Generates 5 random ints between 1 and 100 (exclusive)
        Assert.That(value, Is.InRange(1, 99));
    }

    [Test]
    public void TestWithDoubleRange([Random(-1.0, 1.0, 3)] double value)
    {
        // Generates 3 random doubles between -1.0 and 1.0
        Assert.That(value, Is.InRange(-1.0, 1.0));
    }
}

Distinct Values

[TestFixture]
public class RandomDistinctTests
{
    [Test]
    public void TestWithDistinctValues([Random(1, 10, 5, Distinct = true)] int value)
    {
        // Generates 5 distinct random ints - no value will repeat
        Assert.That(value, Is.InRange(1, 9));
    }
}

Random GUIDs

[TestFixture]
public class RandomGuidTests
{
    [Test]
    public void TestWithRandomGuid([Random(3)] Guid value)
    {
        // Generates 3 random GUIDs
        // Note: Guid does not support min/max range
        Assert.That(value, Is.Not.EqualTo(Guid.Empty));
    }
}

Combined with Other Attributes

[TestFixture]
public class RandomCombinedTests
{
    [Test]
    public void TestWithMultipleRandomParams(
        [Values(1, 2, 3)] int x,
        [Random(-1.0, 1.0, 2)] double d)
    {
        // Creates 6 test cases: 3 x values * 2 random doubles
        Assert.That(d, Is.InRange(-1.0, 1.0));
    }
}

Notes

  1. By default, NUnit creates test cases from all combinations of parameter values (combinatorial). Use [Sequential] to pair values in order instead.
  2. There is no constructor for decimal min/max because .NET does not support decimal in attribute constructors. Use an int or double range instead - values will be converted.
  3. Guid does not support min/max ranges - only the count-only constructor works.
  4. When using Distinct = true, ensure the range is large enough to provide the requested number of distinct values.
  5. Guid support was added in NUnit 4.0.

See Also