The factory class is responsible for generating objects without specifying their type

I manage a factory that specializes in facilitating dependency injection. Here's an example of what it looks like:

import SomeImportantObject from "./SomeImportantObject"
import DataInterface from "./DataInterface"

class NoodleFactory {
  this.dependency: SomeImportantObject
  constructor(dependency: SomeImportantObject) {
    // Setting up dependencies.
    this.dependency = dependency;
  }

  create(data: DataInterface) {
    return new Noodle(data, this.dependency);
  }
}

Recently, as part of ensuring the correctness of the factory in creating objects, I developed a test that closely resembles the following:

data = {
  // Sample data.
}

mockDependency = "a mocked dependency."

testNoodleFactory = new NoodleFactory(mockDependency);

const expected = new Noodle(data, mockDependency);
const actual = testNoodleFactory.create(data);

test("Confirming noodle creation by the factory", () => {
  expect(actual).toMatchObject(expected);
});

However, upon running the test, an error message appears:

    @@ -1,6 +1,6 @@
    - Noodle {
    + Object {

All internal data seems to be aligned correctly.

What might be causing the discrepancy in object types?

Answer №1

Utilize console.log to investigate the output of each function call.

Upon analyzing your code (without running it), I am unable to find a reason for this behavior.

I briefly examined the Jest source code and found the object matcher at this location: https://github.com/facebook/jest/blob/master/packages/expect/src/matchers.ts#L878

This matcher utilizes the iterableEquality and subsetEquality tests from here: https://github.com/facebook/jest/blob/master/packages/expect/src/utils.ts

The toMatchObject method verifies that the input is an object, shares the same constructor (which appears to be causing the issue), and confirms that the compared object has a subset of keys matching those in the original object being tested.

I recommend examining the constructor of the object produced by the Noodle factory function initially.

If you create a Minimal Reproducible Example (MRE) in a GitHub repository, I can review it and follow the code execution path (alternatively, you may do so by inserting console.log statements in the Jest within the node_modules directory).

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