public async Task DeleteJsonAsync_Should_Delete_User_Json_With_Same_IdAsync(string username, Guid jsonId) { Expression <Func <DbJson, bool> > expression = null; _mongoCollectionClient .When(x => x.DeleteOneAsync(username, Arg.Any <Expression <Func <DbJson, bool> > >())) .Do(info => { expression = (Expression <Func <DbJson, bool> >)info[1]; }); await _jsonRepositoryInstance.DeleteJsonAsync(username, jsonId); Expression <Func <DbJson, bool> > expectedExpression = x => x.Id == jsonId; Assert.IsTrue(Lambda.Eq(expectedExpression, expression)); }