public void CallingDefaultConstraintAddsDeleteDefaultConstraintExpressionToContext()
        {
            var collectionMock = new Mock<ICollection<IMigrationExpression>>();

            var contextMock = new Mock<IMigrationContext>();
            contextMock.Setup(x => x.Expressions).Returns(collectionMock.Object);

            var root = new DeleteExpressionRoot(contextMock.Object);
            root.DefaultConstraint();

            collectionMock.Verify(x => x.Add(It.IsAny<DeleteDefaultConstraintExpression>()));
            contextMock.VerifyGet(x => x.Expressions);
        }