(aws-cdk): Default jest testEnvironment setting in init-templates jest.config.js leads to very slow tests

[pkwarren]

The default CDK jest.config.js created by cdk init uses the default testEnvironment setting of jsdom. I don't think CDK tests should need any browser based environment for testing, and when switching to node I see the following locally with some simple tests on a small CDK application:

Before:

✨  Done in 21.57s.

After:

✨  Done in 2.87s.

The tests are generally in the format:

test('stack creates my-function lambda with expected environment variables', () => {
  expectCDK(stack).to(
    haveResource('AWS::Lambda::Function', {
      Environment: {
        Variables: {
          ...
        },
      },
      FunctionName: 'my-function',
    })
  );
});

Reproduction Steps

Create a CDK app with cdk init app --language=typescript. Add some resources (i.e. lambda, subscription filter, dynamo table) and a test that uses haveResource on the stack.

What did you expect to happen?

Test to complete in a reasonable amount of time given the complexity of the CDK app.

What actually happened?

CDK test takes >20s to run.

Environment

• CDK CLI Version : 1.202.0
• Framework Version: Typescript
• Node.js Version: v14.16.1
• OS : MacOS 11.3.1
• Language (Version): TypeScript 4.x

Other

Setting testEnvironment: "node" in jest.config.js reduces the time to run tests close to 10x.

---

This is 🐛 Bug Report

[MrArnoldPalmer]

good callout, made a PR here #14632

[github-actions]

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