Code coverage basics in Node.js - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is code coverage?

Code coverage measures how much of your code is tested by automated tests. It shows which parts of the code ran during testing.

beginner

Name three common types of code coverage.

1. Line coverage: checks if each line of code ran.<br>2. Branch coverage: checks if each decision path ran.<br>3. Function coverage: checks if each function was called.

intermediate

Why is 100% code coverage not always necessary?

Because some code is hard to test or not critical. Also, high coverage doesn't guarantee no bugs, but it helps find many issues.

beginner

How do you generate code coverage reports in Node.js?

You can use tools like 'nyc' (Istanbul) with your test runner. Run tests with coverage enabled to see which code ran.

beginner

What does a coverage report typically show?

It shows percentages of lines, branches, and functions covered. It highlights uncovered code to improve tests.

What does line coverage measure?

A If the code compiles without errors

B If each function was called

C If each line of code was executed during tests

D If each branch decision was tested

Line coverage checks if every line of code ran during testing.

Which tool is commonly used in Node.js for code coverage?

A Jest

B nyc (Istanbul)

C Mocha

D Express

'nyc' is a popular code coverage tool for Node.js, often used with test runners.

Why might 100% code coverage be unrealistic?

A Because some code is unreachable or hard to test

B Because tests are not important

C Because coverage tools are inaccurate

D Because code coverage slows down the app

Some code paths are difficult or unnecessary to test, so 100% coverage is not always practical.

What does branch coverage check?

A If each function was called

B If the code is formatted correctly

C If the code runs without errors

D If each decision path (like if/else) was tested

Branch coverage ensures all decision paths in the code are tested.

What is the main benefit of using code coverage?

A To find untested parts of code and improve test quality

B To make the code run faster

C To reduce the size of the code

D To automatically fix bugs

Code coverage helps identify which parts of code lack tests, improving overall test quality.

Explain what code coverage is and why it is useful in testing Node.js applications.

Think about how you check if your tests run all parts of your code.

Describe how you would set up code coverage reporting in a Node.js project.

Consider the tools and commands you use to see which code your tests cover.