Mock Mongo ObjectId

Showcase of 3 approaches to mocking Mongo ObjectId

Here's the report according to 3 tests:

Identity mocking

const identityObjectId = data => data; (see ./src/identity-object-id.test.js)

Conclusions:

• super simple
• passes toString test, returns right values since 'abc'.toString() === 'abc'
• fails the ObjectId('a') is an object test (it's a string)
• passes ObjectId('a') === ObjectId('a') test, 'a' === 'a'

Naive mocking

See ./src/naive-object-id.test.js

const naiveObjectId = data => {
  return {
    name: data,
    toString: () => data
  };
};

Conclusions:

• More involved
• passes toString test, returns right values since .toString() returns whatever was passed into constructor
• fails the ObjectId('a') === ObjectId('a') test, since toString is a new function
• passes the ObjectId('a') is an object test

Working mock

See ./src/object-id-mock.test.js

const mockObjectId = data => {
  const oid = {
    name: data
  };
  Object.defineProperty(oid, "toString", {
    value: () => data
  });
  return oid;
};

Conclusions:

• Object.defineProperty() hackery...
• passes toString test, returns right values since .toString() returns whatever was passed into constructor
• passes the ObjectId('a') === ObjectId('a') test, since toString is not an enumerable property
• passes the ObjectId('a') is an object test