Mocking Asynchronous Functions with Jest

Mocking is a fundamental skill in testing. It allows you to avoid testing parts of your code that are outside your control, or to get reliable return values from said code.

00:00 - What we'll cover
01:00 - Reviewing the project setup
03:02 - Creating the test
06:24 - Adding async await to pass test
07:17 - Why mock an api request for unit tests
08:32 - Adding jest mock for axios
14:06 - Check if mock function has been called
15:31 - Shorthand for mocking resolved promise value
16:23 - Gotcha for mock state, and how to clear it each test
18:24 - Alternate way of mocking within a test file
20:50 - Wrap-up

Repository for code example:

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#jest #mock #async

[sharonfitzpatrick]

This is by far the best video I've found explaining mocking Jest

[jimmymac]

I will personally hunt down anyone who downvotes this tutorial. Outstanding presentation.

[tachylamurray]

God Bless you or whatever. I lost a whole day trying to figure out how to call my test async. So true how "it might not be so obvious to some" Thank You!

[ShubhamKumar-mkzb]

I prefer blogs over videos, thankyou for making one and very understandable.

[mateuszszaowicz]

This is the best video about mocking I have encountered, it really made me understand how it works. Big thanks to you sir!

[imekachi]

Thank you for taking us into traps and teaching us how to escape/fix them.
Short, precise, and easy to understand, also with sections that you can jump around and quickly learn what you need. 👍 Amazing.

[viridianite]

Thank you so much, Jimmy! You're slowly demystifying testing JS code with Jest for me!

[LeoMuzi]

Thank you so much! This is really useful to understand how mocking works under the hood, helps you thinking of what's going on to figure out issues with testing. Helped me a lot.

[SwOOp_de]

Great video...thanks for explaining jest mocks.

[petergoodey]

We have struggled with axios mocking on a complex React/Typescript project having only recently up-skilled. Best explainer!

[jonathanlinat]

This was the most useful video I ever watched about mocking functions using Jest. You've made it pretty simple to understand the concept. Nice job Jimmy!

[giachan]

this video is short and easy to understand, please make more videos for unit testing, it is helpful for a beginner like me. Thanks!

[arfasaif]

one of the simplest and well-explained clean video of jest mocking so far! thanks!

[Alan.livingston]

Needs to be more stuff of this quality on the net. Most explanations are too simplistic and are aimed at people with no experience.

[gordemn]

Wow I was really struggling with this but got it to work thanks to your videos. Thank you js Jesus

[vikramin]

The way you teach is fantastic! And yes, this is the best video on the topic.👏👏 Thank you so much

[JoseciusDev]

Thanks for this content. (from India
)

[aglowkeys]

Thank you! This was so useful to me. Gonna be watching some more of your Jest videos now. :)

[CristianAndresNietoGarcia]

An excellent resource in my current journey in Unit testing

[emmanuelsackey]

Thank you. You earned a subscriber at "Sanity check" . Awesome bro.