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[MUSIC]

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Hello world.

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Andrew here, JavaScript developer,
lifelong learner and

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teacher here at Treehouse.

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In this workshop, we're going to
be talking about code coverage.

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Code coverage is the healthy
development practice that describes how

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much of a program source code is executed
during the execution of the test sweep.

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So, why should you do code coverage?

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Well, it helps to see how much
testing you're doing in your project.

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It helps you spot parts in your
code that the tests are missing.

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It's also good to show business
stakeholders in a project,

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whether they are a project manager or
clients on a project.

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If you're publishing NPM modules,

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showing your code coverage gives
developers confidence in your module.

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For example, you'd expect
a module with 100% code coverage

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should work better than
a module with only 10%.

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While software with more code coverage
may instill more confidence than software

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without code coverage,

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it doesn't guarantee the quality of
the tests that test the source code.

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For example,
there may be sets in edge cases missing.

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Because test edge cases could be missing,

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there could be some bugs
that could still happen.

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In other words, having 100% code
coverage doesn't ensure good software.

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The till we'll be using for
code coverage is called Istanbul.

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Istanbul is a node module that's
compatible with testing libraries

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like Mocha and Jasmine.

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Istanbul can generate code coverage
reports that are compatible with

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online services like Coveralls and
Codecov.

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You can share your open source
projects code coverage publicly, or

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your internal or
client projects privately.

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In this workshop, we're going to set up
code coverage in a simple calculator app.

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Feel free to clone the app now or download
the zip file attached to this video.