# tsd-lite
> Test your TypeScript types easily.
[](https://npmjs.com/package/tsd-lite)
[](https://github.com/mrazauskas/tsd-lite/blob/main/LICENSE.md)
[](https://github.com/mrazauskas/tsd-lite/actions/workflows/node-ci.yml)
This is a lighter version of [`tsd`](https://npmjs.com/package/tsd). Slightly reworked codebase allows `tsd-lite` to be a tool which simply tests your types.
> **Note** This library is intended for programmatic use only. For an integration with Jest see [`jest-runner-tsd`](https://github.com/jest-community/jest-runner-tsd), if you prefer standalone CLI implementation check [`tsd-lite-cli`](https://github.com/asd-xiv/tsd-lite-cli).
## Motivation
While `tsd` suites perfectly for JavaScript libraries which declare their types in `.d.ts` files, its usage with monorepos written in TypeScript may become [cumbersome](https://github.com/SamVerschueren/tsd/issues/32). `tsd-lite` is an attempt to address these and similar issues.
## Differences from `tsd`
- `tsd-lite` performs only type testing without any additional checks or rules.
- Exposes only general type related assertions: `expectAssignable`, `expectDeprecated`, `expectType` and their counterparts. Currently other APIs (like `expectNever`, `expectDocCommentIncludes` and `printType`) are not implement.
- Comes with no default compiler options.
- Reads TypeScript compiler options from the nearest `tsconfig.json` for each test file (does not read options from `package.json`).
- `tsd-lite` is optionally `strict`. You should add `"strict": true` to the nearest `tsconfig.json` (it can be project or test specific) to use strict assertions.
- [`@tsd/typescript`](https://npmjs.com/package/@tsd/typescript) package is moved to peer dependencies.
- `tsd-lite` allows only programmatic [usage](#usage).
## Install
```bash
yarn add -D tsd-lite @tsd/typescript
# or
npm install -D tsd-lite @tsd/typescript
```
Remember to install `@tsd/typescript`. It is a required peer dependency.
## Usage
```ts
import tsdLite from "tsd-lite";
const { assertionsCount, tsdResults } = tsdLite(
"/absolute/path/to/testFile.test.ts"
);
```
## API Reference
### `tsdLite(testFilePath: string)`
The exported function takes fully resolved path to a test file as an argument and returns an object:
```ts
{
assertionsCount: number;
tsdResults: Array<{
messageText: string | ts.DiagnosticMessageChain;
file?: ts.SourceFile;
start?: number;
}>;
}
```
`tsd-lite` will throw if TS compiler encountered an error while parsing `tsconfig.json` or a syntax error is found while compiling the code.
## License
[MIT](https://github.com/mrazauskas/tsd-lite/blob/main/LICENSE.md)
