joscha / ts-jest-transformer-example

Custom transformer & module mapper with jest & ts-jest

Example: Custom transformer & module mapper with jest & ts-jest

This repository shows how to use custom transformers and module mappers with jest when using ts-jest.

It also shows especially how this works when there is a custom tsconfig to be used for the test environment.

Examples

Have a look at

• ./tools/fileTransformer.js to see how to write a transformer using ts-jest-transformer
• ./tools/stubProxy.ts to see how to write a module mapper
• ./tools/identityProxy.ts to see how to use the identity-obj-proxy in a module mapper

Caveats

• Transformers can not be written in TypeScript, because they are picked up by ts-jest and are not transpiled
• Module mappers have to be written in TypeScript, so the exports end up in the right place
• Put your transformers before the ts-jest preprocessor

Development

Run yarn dev to run the sample test with a disabled jest cache. Have a look at ./tmp to see the generated files (helps you with debugging)