DVA-C02 Question 273
Single answerA developer is building a serverless application using AWS Lambda and wants to implement unit tests to ensure the function behaves as expected. The function interacts with an Amazon DynamoDB table to retrieve data. How can the developer test the function without making actual calls to DynamoDB?
- A
Use AWS X-Ray to simulate DynamoDB responses for the Lambda function.
- B
Use a mock library to simulate the DynamoDB client and define expected responses.
- C
Create a separate DynamoDB table for testing and point the Lambda function to this table.
- D
Enable DynamoDB Streams to capture data changes and replay them during testing.
Show answer and explanation
Correct answer: B
Explanation
Unit testing aims to test the logic of the application in isolation, without dependencies on external systems like DynamoDB. Using a mock library allows developers to simulate the behavior of the DynamoDB client, ensuring the Lambda function's logic can be tested independently and efficiently.
- A. Incorrect.
AWS X-Ray is used for tracing and debugging distributed applications but does not simulate DynamoDB responses. It is not suitable for unit testing.
- B. Correct.
A mock library allows developers to simulate the DynamoDB client and control its responses, enabling unit testing without making actual network calls.
- C. Incorrect.
Creating a separate DynamoDB table for testing involves making real calls to the database, which is not recommended for unit testing as it is slower and less isolated.
- D. Incorrect.
DynamoDB Streams is used for capturing and processing data changes but does not assist in simulating responses for unit testing.