<PackageReference Include="NUnit" Version="4.2.2" />

NUnit.Framework.Is

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