public void GetItemsByCategory_with_invalid_data()
        {
            // arrange
            var mclient = GetMockClient(out Mock <IMongoCollection <PasswordStoreModel> > mcollection);
            var mrepo   = new PassStoreMongo(mclient.Object);

            // act and assert
            Assert.Throws <ArgumentNullException>(() => mrepo.GetItemsByCategory(null)
                                                  .GetAwaiter().GetResult());
        }
        public void GetItemsByCategory_with_valid_store_model()
        {
            // arrange
            var mclient = GetMockClient(out Mock <IMongoCollection <PasswordStoreModel> > mcollection);
            var mrepo   = new PassStoreMongo(mclient.Object);

            // act
            var rslt = mrepo.GetItemsByCategory("key-217533")
                       .GetAwaiter().GetResult();

            // assert
            mclient.VerifyAll();
            mcollection.Verify(mc => mc.AggregateAsync(It.IsAny <PipelineDefinition <PasswordStoreModel, PasswordsCategory> >(),
                                                       default(AggregateOptions), default(CancellationToken)),
                               Times.Once);
        }