Type Assertions

Assertions to test your TypeScript types.

Usage

Define a type-tests.ts file and you can make assertions like:

import * as ta from 'type-assertions';
 
ta.assert<ta.Not<ta.Equal<{x: 1}, never>>>();
ta.assert<ta.Not<ta.Equal<never, {x: 1}>>>();
 
ta.assert<ta.Not<ta.Equal<{x: 1}, {y: 1}>>>();
ta.assert<ta.Not<ta.Equal<{y: 1}, {x: 1}>>>();
 
ta.assert<ta.Extends<{x: 1}, any>>();
ta.assert<ta.Not<ta.Extends<any, {x: 1}>>>();
 
ta.assert<ta.UnionIncludesExact<string | number, string>>();
ta.assert<ta.Not<ta.UnionIncludesExact<string | number, 'hello'>>>();
ta.assert<ta.Not<ta.UnionIncludesExact<number, 'hello'>>>();

When you run the build, you will get errors in typesctipt if any of your assertions are not valid.

License

MIT