public async void VerifyFixExpirationDate() { DateTime fixedExpiration = DateTime.UtcNow.AddDays(30); mockDataHandler.Setup(m => m.GetData <Batch>(DataSource.Batches)) .ReturnsAsync(batchList); mockDataHandler.Setup( m => m.WriteData(DataSource.Batches, It.IsAny <List <Batch> >()) ).Returns(Task.CompletedTask); Batch udpatedBatch = await dataAccess.FixExpirationDate(testBatch1.Id, fixedExpiration); Assert.Equal(fixedExpiration, udpatedBatch.Expiration); mockDataHandler.Verify(m => m.GetData <Batch>(DataSource.Batches), Times.Once); mockDataHandler.Verify(m => m.WriteData(DataSource.Batches, It.IsAny <List <Batch> >()), Times.Once); }