freeCodeCamp/curriculum/challenges/english/06-quality-assurance/quality-assurance-and-testing-with-chai/test-if-an-object-is-an-instance-of-a-constructor.md

---
id: 587d824e367417b2b2512c57
title: Test if an Object is an Instance of a Constructor
challengeType: 2
forumTopicId: 301605
dashedName: test-if-an-object-is-an-instance-of-a-constructor
---

# --description--

As a reminder, this project is being built upon the following starter project on [Replit](https://replit.com/github/freeCodeCamp/boilerplate-mochachai), or cloned from [GitHub](https://github.com/freeCodeCamp/boilerplate-mochachai/).

`#instanceOf` asserts that an object is an instance of a constructor.

# --instructions--

Within `tests/1_unit-tests.js` under the test labelled `#18` in the `Objects` suite, change each `assert` to either `assert.instanceOf` or `assert.notInstanceOf` to make the test pass (should evaluate to `true`). Do not alter the arguments passed to the asserts.

# --hints--

All tests should pass.

```js
(getUserInput) =>
  $.get(getUserInput('url') + '/_api/get-tests?type=unit&n=17').then(
    (data) => {
      assert.equal(data.state, 'passed');
    },
    (xhr) => {
      throw new Error(xhr.responseText);
    }
  );
```

You should choose the correct method for the first assertion - `instanceOf` vs. `notInstanceOf`.

```js
(getUserInput) =>
  $.get(getUserInput('url') + '/_api/get-tests?type=unit&n=17').then(
    (data) => {
      assert.equal(
        data.assertions[0].method,
        'notInstanceOf',
        'myCar is not an instance of Plane'
      );
    },
    (xhr) => {
      throw new Error(xhr.responseText);
    }
  );
```

You should choose the correct method for the second assertion - `instanceOf` vs. `notInstanceOf`.

```js
(getUserInput) =>
  $.get(getUserInput('url') + '/_api/get-tests?type=unit&n=17').then(
    (data) => {
      assert.equal(
        data.assertions[1].method,
        'instanceOf',
        'airlinePlane is an instance of Plane'
      );
    },
    (xhr) => {
      throw new Error(xhr.responseText);
    }
  );
```

You should choose the correct method for the third assertion - `instanceOf` vs. `notInstanceOf`.

```js
(getUserInput) =>
  $.get(getUserInput('url') + '/_api/get-tests?type=unit&n=17').then(
    (data) => {
      assert.equal(
        data.assertions[2].method,
        'instanceOf',
        'everything is an Object in JavaScript...'
      );
    },
    (xhr) => {
      throw new Error(xhr.responseText);
    }
  );
```

You should choose the correct method for the fourth assertion - `instanceOf` vs. `notInstanceOf`.

```js
(getUserInput) =>
  $.get(getUserInput('url') + '/_api/get-tests?type=unit&n=17').then(
    (data) => {
      assert.equal(
        data.assertions[3].method,
        'notInstanceOf',
        'myCar.wheels is not an instance of String'
      );
    },
    (xhr) => {
      throw new Error(xhr.responseText);
    }
  );
```

# --solutions--

```js
/**
  Backend challenges don't need solutions, 
  because they would need to be tested against a full working project. 
  Please check our contributing guidelines to learn more.
*/
```