assert-typescript-errors

Automatically verify that certain test files fail to pass TypeScript type checks.

This package checks the output from TypeScript's compiler (with the --pretty flag expected to be false) and ensures that it matches with the line numbers you specify.

Usage

As a module

import { exec } from 'child_process';
import { assertTypeScriptErrors } from 'assert-typescript-errors';

/**
 * Specify the lines that should have errors in your test files.
 */
const assertions = {
    'test/type-test.ts': [
        29, // Individual line numbers can be used
        '57-58', // Ranges of line numbers can also be specified. Equivalent to 57, 58.
    ],
    'test/type-test-two.ts': [31, 39, '45-51'],
};

exec('tsc --pretty false', (err, stdout) => {
    assertTypeScriptErrors(stdout, assertions).catch(console.error);
});

From the command line

echo '{ "type-test.ts": [29, "56-60"] }' > assertions.json
tsc --pretty false | assert-ts-errors assertions.json