Clean up test fixtures

Question

I have a CloudFormation stack that defines a GraphQL API powered by DynamoDB. I would like to run a test script that:

• Creates a standard set of fixtures.
• Runs various tests, including creating, modifying, and deleting data.
• Deletes all of the fixtures and any other objects created during the test.

The “clean way” to do this would be to create a new stage for the tests, but this is extremely time-consuming (in terms of wall-clock time spent waiting for the result).

The “hard way” would be to keep precise track of every DynamoDB record created during the testing process and then delete them afterward one by one (and/or using many batch updates). This would be a huge pain to code, and the likelihood of error is very high.

An intermediate approach would be to use a dedicated pre-existing stage for integration tests, wipe it clean at the end of the tests, and make sure that only one set of tests is running at a time. This would require writing a script to manually clear out the tables, which sounds moderately less tedious and error-prone than the “hard way”.

Is there an established best practice for this? Are there other approaches I haven't considered?

Answer 1

How long does it take to deploy the stack?

If it is only a small portion of the time that takes to run the tests use the "clean way", otherwise use the intermediate approach of having a dedicated test stack already deployed.

You don't have to write scripts. I actually wrote a testing library for this purpose exactly: https://github.com/erezrokah/aws-testing-library/blob/master/src/jest/README.md#tohaveitem

Usage example (TypeScript):

import { clearAllItems } from 'aws-testing-library/lib/utils/dynamoDb';
import { invoke } from 'aws-testing-library/lib/utils/lambda';

describe('db service e2e tests', () => {
  const region = 'us-east-1';
  const table = 'db-service-dev';
  beforeEach(async () => {
    await clearAllItems(region, table);
  });

  afterEach(async () => {
    await clearAllItems(region, table);
  });

  test('should create db entry on lambda invoke', async () => {
    const result = await invoke(region, 'db-service-dev-create', {
      body: JSON.stringify({ text: 'from e2e test' }),
    });
    const lambdaItem = JSON.parse(result.body);

    expect.assertions(1);
    await expect({ region, table, timeout: 0 }).toHaveItem(
      { id: lambdaItem.id },
      lambdaItem,
    );
  });
});

If you do write the scripts yourself you might need to consider eventual consistency and retry (as the data might not be available directly after write)