How do you unit test a custom param decorator?

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Current behavior

How can I test the result of a parameter decorator created using createParamDecorator from @nestjs/common?

Example

Given the following simple decorator how can I test that it correctly returns “user” from the req object?

export const CurrentUser = createParamDecorator((_, req) => req.user);

I know one option would be to separate the factory function that I’m passing in and just test that, but I’d really rather not export it if that’s possible.

Issue Analytics

State:
Created 5 years ago
Comments:6 (1 by maintainers)

Top GitHub Comments

9reactions

itslennycommented, Aug 30, 2018

I figured out a solution from digging through the createParamDecorator that source. Seems to work pretty well. Is there a better way of doing this?


function getParamDecoratorFactory(decorator: Function) {
  class Test {
    public test(@decorator() value) { }
  }

  const args = Reflect.getMetadata(ROUTE_ARGS_METADATA, Test, 'test');
  return args[Object.keys(args)[0]].factory;
}

/// Usage

const factory = getParamDecoratorFactory(CurrentUser);
const mockUser = {};
const result = factory(null, {user: mockUser));

expect(result).toBe(mockUser);

2reactions

danieldaeschlecommented, Jan 22, 2019

import { ROUTE_ARGS_METADATA } from '@nestjs/common/constants';