Runs tests on TypeScript definition files

0.9.6  •  Updated 7 months ago  •  by microsoft  •  MIT License

dtslint tests a TypeScript declaration file for style and correctness. It will install typescript and tslint for you, so this is the only tool you need to test a type definition.

Lint rules new to dtslint are documented in the docs directory.


If you are working on DefinitelyTyped, read the DefinitelyTyped README.

If you are writing the library in TypeScript, don’t use dtslint. Use --declaration to have type definitions generated for you.

If you are a library author, read below.

Add types for a library (not on DefinitelyTyped)

dts-gen may help, but is not required.

Create a types directory. (Name is arbitrary.) Add "types": "types" to your package.json. Read more on bundling types here.


Only index.d.ts needs to be published to NPM. Other files are just for testing. Write your type definitions here. Refer to the handbook or dts-gen's templates for how to do this.


    "compilerOptions": {
        "module": "commonjs",
        "lib": ["es6"],
        "noImplicitAny": true,
        "noImplicitThis": true,
        "strictNullChecks": true,
        "strictFunctionTypes": true,
        "noEmit": true,

        // If the library is an external module (uses `export`), this allows your test file to import "mylib" instead of "./index".
        // If the library is global (cannot be imported via `import` or `require`), leave this out.
        "baseUrl": ".",
        "paths": { "mylib": ["."] }

You may extend "lib" to, for example, ["es6", "dom"] if you need those typings. You may also have add "target": "es6" if using certain language features.


If you are using the default rules, this is optional.

If present, this will override dtslint's default settings. You can specify new lint rules, or disable some. An example:

    "extends": "dtslint/dtslint.json", // Or "dtslint/dt.json" if on DefinitelyTyped
    "rules": {
        "semicolon": false,
        "indent": [true, "tabs"]


You can have any number of test files you want, with any names. See below on what to put in them.

Write tests

A test file should be a piece of sample code that tests using the library. Tests are type-checked, but not run. To assert that an expression is of a given type, use $ExpectType. To assert that an expression causes a compile error, use $ExpectError. (Assertions will be checked by the expect lint rule.)

import { f } from "my-lib"; // f is(n: number) => void

// $ExpectType void

// Can also write the assertion on the same line.
f(2); // $ExpectType void

// $ExpectError

Specify a TypeScript version

Normally packages will be tested using TypeScript 2.0. To use a newer version, specify it by including a comment like so:

// TypeScript Version: 2.1

For DefinitelyTyped packages, this should go just under the header (on line 5). For bundled typings, this can go on any line (but should be near the top).

Run tests

  • npm install --save-dev dtslint
  • Add to your package.json scripts: "dtslint": "dtslint types"
  • npm run dtslint


  • --localTs

Use your locally installed version of TypeScript.

dtslint --localTs node_modules/typescript/lib types
  • --expectOnly

Disable all the lint rules except the one that checks for type correctness.

dtslint --expectOnly types



npm link . # Global 'dts-lint' should now refer to this.
npm run watch


Use npm run test to run all tests. To run a single test: node node_modules/tslint/bin/tslint --rules-dir bin/rules --test test/expect.


production branch

npm run push-production

This script merges changes from master into production and updates the bin/ directory. The production branch is a dependency of DefinitelyTyped and types-publisher.


  1. Update package.json
  2. Follow publish steps except for the git push at the end.
  3. Make sure you are logged in to npm as typescript.
  4. npm publish

Code of Conduct

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.


I’m getting an error about a missing typescript install.

Error: Cannot find module '/node_modules/dtslint/typescript-installs/3.1/node_modules/typescript`

Package lock files such as yarn.lock and package-lock.json may cause this issue because of our github dependency on "definitelytyped-header-parser": "github:Microsoft/definitelytyped-header-parser#production", which contains the list of typescript versions to install. To fix this, try deleting your lock file and re-installing.


Weekly Downloads



Last ver 7 months ago
Created 3 years ago
Last commit 5 months ago
3 days between commits


Node version: 12.9.1
183.9K unpacked


MIT License
OSI Approved
0 vulnerabilities


32 contributors
Andy Hanson
237 commits, 90 merges, 81 PRs
Works at Microsoft
Nathan Shively-Sanders
114 commits, 33 merges, 20 PRs
Works at Microsoft
Daniel Rosenwasser
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Works at Microsoft
Ron Buckton
4 commits, 1 merges, 1 PRs
Works at Microsoft
Anders Hejlsberg
2 commits, 1 merges, 1 PRs
Works at Microsoft
Sebastian Silbermann
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