freeCodeCamp/guide/english/certifications/information-security-and-quality-assurance/quality-assurance-and-testing-with-chai/test-if-a-variable-or-function-is-defined/index.md

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title: Test if a Variable or Function is Defined
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# Test if a Variable or Function is Defined

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## Problem Explanation
To begin, locate the file "tests/1_unit_tests.js".

This file contains multiple suites of tests for the project, and this challenge requires you to make the tests in ``` /** 2 */``` pass.


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## Hints

### Hint 1

The lines in the test should be changed from `assert.fail()` to either `assert.isDefined()` or `assert.isUndefined()`.


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## Solutions

<details><summary>Solution #1(Click to Show/Hide)</summary>

```js
/** 2 - Use assert.isDefined() or assert.isUndefined() to make the tests pass. **/
test('#isDefined, #isUndefined', function() {
  assert.isDefined(null, 'null is not undefined');
  assert.isUndefined(undefined, 'undefined IS undefined');
  assert.isDefined('hello', 'a string is not undefined');
});
```
</details>