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node.jsmongoosejestjsmongoose-schema

How to write Unit test for a method which returns anonymous function

I am writing unit test case(jest) for a method which return anonymous function. for the function i need to pass entity name and for anonymous function, it takes this(mongoose response) and next(express) as a arguments. how to mock or pass value to this while calling the validate method?

Method

  validatesss(entityName: string) {
    return async function (this: any, next: HookNextFunction) {
      const sequence = await metadataModel.getIncrementedSequence(entityName);
      this.set({ [entityName + '_no']: sequence });
      next();
    };
  }
Solution

  • this can be provided to a function with call or apply:

    let next = jest.fn();
let set = jest.fn();
let fn = obj.validatesss('foo');
expect(fn).toEqual(expect.any(Function));
await fn.call({ set }, next);
expect(set).toBeCalledWith({ foo_no: ... });
expect(next).toBeCalledWith();