<PackageReference Include="NUnit" Version="4.2.1" />

Is

public abstract class Is
Helper class with properties and methods that supply a number of constraints used in Asserts.
using NUnit.Framework.Constraints; using System; using System.Collections; using System.Runtime.CompilerServices; namespace NUnit.Framework { [System.Runtime.CompilerServices.NullableContext(1)] [System.Runtime.CompilerServices.Nullable(0)] public abstract class Is { public static ConstraintExpression Not => new ConstraintExpression().Not; public static ConstraintExpression All => new ConstraintExpression().All; public static NullConstraint Null => new NullConstraint(); public static DefaultConstraint Default => new DefaultConstraint(); public static TrueConstraint True => new TrueConstraint(); public static FalseConstraint False => new FalseConstraint(); public static GreaterThanConstraint Positive => new GreaterThanConstraint(0); public static LessThanConstraint Negative => new LessThanConstraint(0); public static EqualConstraint Zero => new EqualConstraint(0); public static NaNConstraint NaN => new NaNConstraint(); public static EmptyConstraint Empty => new EmptyConstraint(); public static WhiteSpaceConstraint WhiteSpace => new WhiteSpaceConstraint(); public static UniqueItemsConstraint Unique => new UniqueItemsConstraint(); public static XmlSerializableConstraint XmlSerializable => new XmlSerializableConstraint(); public static CollectionOrderedConstraint Ordered => new CollectionOrderedConstraint(); public static EqualConstraint EqualTo([System.Runtime.CompilerServices.Nullable(2)] object expected) { return new EqualConstraint(expected); } public static SameAsConstraint SameAs([System.Runtime.CompilerServices.Nullable(2)] object expected) { return new SameAsConstraint(expected); } public static GreaterThanConstraint GreaterThan(object expected) { return new GreaterThanConstraint(expected); } public static GreaterThanOrEqualConstraint GreaterThanOrEqualTo(object expected) { return new GreaterThanOrEqualConstraint(expected); } public static GreaterThanOrEqualConstraint AtLeast(object expected) { return new GreaterThanOrEqualConstraint(expected); } public static LessThanConstraint LessThan(object expected) { return new LessThanConstraint(expected); } public static LessThanOrEqualConstraint LessThanOrEqualTo(object expected) { return new LessThanOrEqualConstraint(expected); } public static LessThanOrEqualConstraint AtMost(object expected) { return new LessThanOrEqualConstraint(expected); } public static ExactTypeConstraint TypeOf(Type expectedType) { return new ExactTypeConstraint(expectedType); } public static ExactTypeConstraint TypeOf<[System.Runtime.CompilerServices.Nullable(2)] TExpected>() { return new ExactTypeConstraint(typeof(TExpected)); } public static InstanceOfTypeConstraint InstanceOf(Type expectedType) { return new InstanceOfTypeConstraint(expectedType); } public static InstanceOfTypeConstraint InstanceOf<[System.Runtime.CompilerServices.Nullable(2)] TExpected>() { return new InstanceOfTypeConstraint(typeof(TExpected)); } public static AssignableFromConstraint AssignableFrom(Type expectedType) { return new AssignableFromConstraint(expectedType); } public static AssignableFromConstraint AssignableFrom<[System.Runtime.CompilerServices.Nullable(2)] TExpected>() { return new AssignableFromConstraint(typeof(TExpected)); } public static AssignableToConstraint AssignableTo(Type expectedType) { return new AssignableToConstraint(expectedType); } public static AssignableToConstraint AssignableTo<[System.Runtime.CompilerServices.Nullable(2)] TExpected>() { return new AssignableToConstraint(typeof(TExpected)); } public static CollectionEquivalentConstraint EquivalentTo(IEnumerable expected) { return new CollectionEquivalentConstraint(expected); } public static CollectionSubsetConstraint SubsetOf(IEnumerable expected) { return new CollectionSubsetConstraint(expected); } public static CollectionSupersetConstraint SupersetOf(IEnumerable expected) { return new CollectionSupersetConstraint(expected); } public static SamePathConstraint SamePath(string expected) { return new SamePathConstraint(expected); } public static SubPathConstraint SubPathOf(string expected) { return new SubPathConstraint(expected); } public static SamePathOrUnderConstraint SamePathOrUnder(string expected) { return new SamePathOrUnderConstraint(expected); } public static RangeConstraint InRange(object from, object to) { return new RangeConstraint(from, to); } public static AnyOfConstraint AnyOf([System.Runtime.CompilerServices.Nullable(2)] params object[] expected) { if (expected == null) expected = new object[1]; return new AnyOfConstraint(expected); } public static AnyOfConstraint AnyOf(ICollection expected) { return new AnyOfConstraint(expected); } } }