public void SortBy_WhenExpressionAllreadyBeenAssigned_ThrowsSisoDbException() { var sortingParserFake = new Mock <ISortingParser>(); sortingParserFake .Setup(f => f.Parse(It.IsAny <Expression <Func <MyClass, object> >[]>())) .Returns(new Mock <IParsedLambda>().Object); var builder = CreateBuilderWithFakes(); builder.SortingParser = sortingParserFake.Object; var expression = Reflect <MyClass> .ExpressionFrom <object>(m => m.Int1); builder.SortBy(expression); Assert.Throws <SisoDbException>(() => builder.SortBy(expression)); }