File Structure

This page covers several project structure strategies. Pick the one that suits your needs.

Dedicated Directory

Keeping type test files in a dedicated directory is the recommended approach. It separates concerns and makes isolation straightforward.

- - MethodLikeKeys.tst.ts
  - tsconfig.json
- MethodLikeKeys.ts
package.json
tsconfig.json

The root tsconfig.json holds the compiler configuration of the project. Extend from it and reuse the configuration for type testing:

./src/__typetests__/tsconfig.json


{
  "extends": "../../tsconfig.json",
  "compilerOptions": {
    "noEmit": true,
    "strict": true,
    "types": []
  },
  "include": ["./"],
  "exclude": []
}

This configuration prevents loading global scope typings from @types/* packages. It includes only the files needed for type testing.

By convention, unit tests are suffixed with .test.* and type tests with .tst.*. The latter ones are only statically analyzed and are not meant to be executed, hence the missing e in the suffix.

Shared Directory

Unit and type test files can also share a single directory:

- - MethodLikeKeys.tst.ts
  - secondItem.test.ts
  - tsconfig.json
- MethodLikeKeys.ts
- secondItem.ts
package.json
tsconfig.json
tstyche.json

Keep the TSConfig as focused as possible to avoid global typings leaking into your type tests:

./src/__tests__/tsconfig.json


{
  "extends": "../../tsconfig.json",
  "compilerOptions": {
    "noEmit": true,
    "strict": true,
    "types": [] // prefer explicitly importing testing APIs
  },
  "include": ["./"],
  "exclude": []
}

Next to Source Files

Isolation of type tests placed next to source files requires a bit more configuration. A project structure could look like this:

- MethodLikeKeys.ts
- MethodLikeKeys.tst.ts
- secondItem.ts
- secondItem.test.ts
package.json
tsconfig.json
tsconfig.test.json
tstyche.json

The references field can be used to define the project in the root tsconfig.json:

./tsconfig.json


{
  "compilerOptions": {
    // ...
    "composite": true
  },
  "include": ["./src"],
  "exclude": ["**/*.test.*", "**/*.tst.*"],
  "references": [{ "path": "./tsconfig.test.json" }]
}

tsconfig.test.json can then extend it:

./tsconfig.test.json


{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "strict": true,
    "types": [] // prefer explicitly importing testing APIs
  },
  "exclude": []
}