Should BatchWrite<T> implement an interface?

[safv12]

I'm trying to write a unit test to validate the BatchWrite.Execute invocation, but I'm struggling with the mock of the CreateBatchWrite<T> method because I'm not able to instantiate the BatchWrite<T> class.

I'm using Moq to build the mocks, the code looks like:

this.dynamoDbMock
    .Setup(m => m.CreateBatchWrite<SomeType>(It.IsAny<DynamoDBOperationConfig>()))
    .Returns(Mock.Of<BatchWrite<SomeType>>());

But the Returns part is throwing an error because the BatchWrite class does not have a default constructor.

Possible Solution

I think is a good idea to define an interface for the BatchWrite class. In this way, the unit test will be easier to write.

public class BatchWrite<T> : BatchWrite, IBatchWriteOperations

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[Kralizek]

@ashishdhingra any comment on this? This is just one of many issues regarding the hard testability of code using DynamoDB.

[ashishdhingra]

@ashishdhingra any comment on this? This is just one of many issues regarding the hard testability of code using DynamoDB.

@Kralizek Some DynamoDB revamp work is planned in the coming sprints and this feature request might be included as well. We would post any updates here.

[jakubbujak]

This is one of the worst libraries regarding testability. Shame on you Amazon, shame 😡

[Kilowhisky]

I just ran into this as well. Can't test any data layer code at all because of this.

[rferreiraLGC]

I am also unable to run my tests due to this.

[rynkadink]

+1
This seems to have been designed without testability in mind, how can we test any data layer code when using this lib?

[Cussa]

Any news on that?

[stitcharg]

I just found the same problem :(

[Kralizek]

Still waiting for the rework...

[LBognanni]

+1, I worked around this by using the nullabilty operator when interacting with the BatchWrite object (ie batch?.AddPutItem(thing))

I would also contend that the detail of BatchWrite should be ideally be hidden for the consumer and the dynamo context should expose something like SaveAsync<T>(IEnumerable<T> things) that handles batching internally

[96malhar]

Hello, we have been working on the V4 of the AWS SDK for .NET. We have added the ability to mock various DynamoDB operations by adding interfaces in both the Data Model mode and Document Model mode in DynamoDB.

Refer to this PR - #3450

Specifically for the BatchWrite<T> class, it now implements the IBatchWrite<T> interface which can be mocked inside unit tests.

This feature is available in the AWSSDK.DynamoDBv2 Version 4.0.0-preview.2

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