TheoryAttribute public class TheoryAttribute : CombiningStrategyAttribute, ITestBuilder, IImplyFixture Indicates that a test method is a theory and can be run multiple times with different input data. Documentation Code using NUnit.Framework.Interfaces; using NUnit.Framework.Internal.Builders; using System; namespace NUnit.Framework { [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)] public class TheoryAttribute : CombiningStrategyAttribute, ITestBuilder, IImplyFixture { public TheoryAttribute(bool searchInDeclaringTypes = false) : base(new CombinatorialStrategy(), new ParameterDataProvider(new DatapointProvider(searchInDeclaringTypes), new ParameterDataSourceProvider())) { } } }