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So we learned that testing might make sense,

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how do we test then?

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We need two tools to write good tests and be able to test our react application.

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The first tool is the test runner,

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this is basically a tool which is responsible for executing our tests

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so for running the code, test code and providing a validation library which in the end is a library which allows

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us to do comparations and potentially throw some errors.

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The idea behind unit tests is that they don't run in the browser but instead with nodeJS though often

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emulated to be in a browser environment with the help of specific javascript packages. The test runner

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then is the core tool which simply executes our code using that environment

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and the good thing is create react app already comes with a pre-configured testing environment

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we can build up on.

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So that's the test runner and we will use jest in this course, jest is already installed in the app

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created with create react app and is a popular javascript testing tool which is not limited to react

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but often used in react apps. Now running the test is one thing, when working with reacting components,

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we also need a way of emulating these components, so basically mounting them to some non-existent dom you

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could say and then traversing our components and we want to do this in an efficient quick way without

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having to actually create that whole component tree which might also introduce some side effects.

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For this, we need testing utilities which help us with testing and there, we specifically need the just

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described help to simulate the react app, mount components and dig into that dom which is created with react.

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In this course we could you as react test utils, that's the official utility tool but there's another tool

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which became more and more important and interesting and is also suggested by the react team

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amd that's enzyme. Enzyme is a tool developed by AirBnB,

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they use react in a lot of their projects and they share this tool which makes it easy to mount components

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and then navigate through them

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and I will of course show you how to use both tools, jest and enzyme in this course.

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So these are the testing tools, that leaves us only with one question, what should we test?