.Net Core DynamodDB unit testing with XUnit

Question

Using C#, .net core 2.0, dynamo db

I have my web api, that interact with my dynamo db database having both Get and Post methods.

Example of Mehthod:

    [HttpGet("api/data")]
    public async Task<List<string>> GetAllData(string userId, string type, string status)
    {
        var creds = new BasicAWSCredentials(awsId, awsPassword);
        var dynamoClient = new AmazonDynamoDBClient(creds, dynamoRegion);
        var context = new DynamoDBContext(dynamoClient);
        List<ScanCondition> conditions = new List<ScanCondition>();
        conditions.Add(new ScanCondition("UserId", ScanOperator.Equal, userId));
        conditions.Add(new ScanCondition("Type", ScanOperator.Equal, type));
        conditions.Add(new ScanCondition("Status", ScanOperator.Equal, status));

        var results = await context.ScanAsync<Common.Job>(conditions, new DynamoDBOperationConfig() { OverrideTableName = MyDynamoTable }).GetRemainingAsync();
        return results.Select(x => x.UpdatedBy.ToLower()).ToList();
    }

Now I want to write unit/integration tests for my api methods. Earlier I had used NUnit but with .net core 2.0 I believe we have to use XUnit: https://xunit.github.io/docs/getting-started-dotnet-core

Setting up Xunit in my project should not be an issue.

I wanted to know how can I write test which involve dynamo db here. This is the first time I am using any AWS service here.

So bascially I need to know how can I mock up a aws connection, dynamo db and then use various params as shown in my method above.

I could not find much details or any earlier helpful post on this topic so posting one here.

---

If aws dynamo db part is not testable. Can anyone share the example of xunit test where we can test the params may be and see the expected result?

Answer 1

AWS SDK work with interfaces. You can mock interface IAmazonDynamoDB easily. But try to do it with dependecy injection-ish. Much better.

Something like

private readonly IAmazonDynamoDB dynamodbClient;
private readonly IDynamoDBContext context;

public MyDynamodbHandler(IAmazonDynamoDB client)
{
    this.dynamodbClient = client;
    this.context = new DynamoDBContext(client);
}

[HttpGet("api/data")]
public async Task<List<string>> GetAllData(string userId, string type, string status)
{

    List<ScanCondition> conditions = new List<ScanCondition>();
    conditions.Add(new ScanCondition("UserId", ScanOperator.Equal, userId));
    conditions.Add(new ScanCondition("Type", ScanOperator.Equal, type));
    conditions.Add(new ScanCondition("Status", ScanOperator.Equal, status));

    var results = await this.context.ScanAsync<Common.Job>(conditions, new DynamoDBOperationConfig() { OverrideTableName = MyDynamoTable }).GetRemainingAsync();
    return results.Select(x => x.UpdatedBy.ToLower()).ToList();
}

So every function uses the injected IAmazonDynamoDB. All you have to do is to mock this instance at the beginning

Such as dynamodbClientMock = new Mock();

Then use this mock to initiate MyDynamodbHandler class

var dynamodbHandler = new MyDynamodbHandler(dynamodbClientMock);
dynamodbHandler.GetAllData();