How to subvert typings of external-facing class constructor to test validation code-CodePudding

I have an external/outward facing class. It contains input-validation code for instances where the library is imported into a JS environment (read: an environment that does not support type checking).

I am attempting to write unit tests specific to that validation code.

// function-token.ts;

// ...

export default class FunctionToken extends Token {
  constructor(token: IFunctionToken) {
    if (token == null) {
      throw new Error('token must be specified');
    }
    
    // ...

  }
}

Currently when I attempt to write a jestjs test for the validation code, the check fails due to typings:

// function-token.spec.ts

import FunctionToken from 'function-token';

test('throws an error when token is nullish', function () {
  // Expected 1 arguments, but got 0 - An argument for 'token' was not provided
  expect(() => new FunctionToken()).toThrow();

  // Argument of [undefined|null] is not assignable to IFunctionToken
  expect(() => new FunctionToken(undefined)).toThrow();
  expect(() => new FunctionToken(null)).toThrow();
});

How do I go about writing a test to subvert the type check with jestjs ts-jest?

Note: Changing the underlying class's typing does not make sense as the validation is specific to cases where there is no type checking or enforcement.

CodePudding user response：

Not sure how you'll get the parameterless call, but I think this is redundant because it defaults to undefined anyway. By casting the arguments to any you can bypass the parameter typings.

expect(() => new FunctionToken(undefined as any)).toThrow();
expect(() => new FunctionToken(null as any)).toThrow();

Alternativly you could just add // @ts-nocheck in testfiles concerning guard clauses.