freeCodeCamp/guide/english/certifications/information-security-and-quality-assurance/quality-assurance-and-testing-with-chai/test-if-an-object-is-an-instance-of-a-constructor/index.md

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Test if an Object is an Instance of a Constructor

Test if an Object is an Instance of a Constructor

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Problem Explanation

To begin, locate the file "tests/1_unit_tests.js" and scroll to the suite of tests for 'Objects'.

This file contains multiple suites of tests for the project, and this challenge requires you to make the tests in /** 18 */ pass.

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Hints

Hint 1

The challenge uses objects defined above the tests. Look closely at both, and determine whether the object is an instance of the type being compared against in the assertion.

Hint 2

Check the error messages to determine if your understanding of the object's instance was correct.

Hint 3

The lines in the test should be changed from assert.fail() to either assert.instanceOf() or assert.notInstanceOf().

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Solutions

Solution 1 (Click to Show/Hide)

test('#instanceOf, #notInstanceOf', function() {
  /** 18 #instanceOf asserts that an object is an instance of a constructor **/
  // Use #instanceOf or #notInstanceOf where appropriate
  assert.notInstanceOf(myCar, Plane);
  assert.instanceOf(airlinePlane, Plane);
  assert.instanceOf(airlinePlane, Object, 'everything is an Object');
  assert.notInstanceOf(myCar.wheels, String);
});