assert-throws-async

Node's builtin assert.throws does not work very well with rejecting promises or (equivalently) async functions.

This wrapper fixes this.

It also allows you to pass both validation functions and constructors to compare with as I got sick of typing e instanceof MyError in my validation functions.

Examples:

const assertThrows = require('assert-throws-async'); 
 
class MyError extends Error { }
const naughtyFunction = () => {
    return Promise.reject(new MyError('waaat'));
}
 
//...
 
assertThrows(naughtyFunction, MyError, 'waaat');

Usage:

assertThrows(f: Function, errorCheck: string | RegExp | ((Error) => boolean));

Runs f().

If it throws or returns a promise that rejects with e:

• if errorCheck is a string or RegExp, check e.message against errorCheck
• If errorCheck is a function, run errorCheck(e).

If either of these checks are unsuccesful, re-throw e.

If f does not throw e, throw an AssertionError('Expected to throw.').

assertThrows(f: Function, ErrorType: class<Error>);

Runs f().

If it throws or returns a promise that rejects with e:

• if e is not an instance of ErrorType, re-throw e.

If f does not throw e, throw an AssertionError('Expected to throw.').

assertThrows(f: Function, ErrorType: class<Error>, errorCheck: string | RegExp | ((Error) => boolean) );

Combines both the above checks. The ErrorType check is executed first.