<PackageReference Include="NUnit" Version="4.3.2" />

NUnit.Framework.Has

public abstract class Has
Helper class with properties and methods that supply a number of constraints used in Asserts.
namespace NUnit.Framework { public abstract class Has { public static ConstraintExpression No { get; } public static ConstraintExpression All { get; } public static ConstraintExpression Some { get; } public static ConstraintExpression None { get; } public static ItemsConstraintExpression One { get; } public static ResolvableConstraintExpression Length { get; } public static ResolvableConstraintExpression Count { get; } public static ResolvableConstraintExpression Message { get; } public static ResolvableConstraintExpression InnerException { get; } public static ItemsConstraintExpression Exactly(int expectedCount); public static ResolvableConstraintExpression Property(string name); public static ResolvableConstraintExpression Attribute(Type expectedType); public static ResolvableConstraintExpression Attribute<[System.Runtime.CompilerServices.Nullable(2)] T>(); public static SomeItemsConstraint Member(object expected); public static ConstraintExpression ItemAt(params object[] indexArgs); protected Has(); } }