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Don't use fixtures in Cypress and unit tests- use factories

Dan Greene on September 18, 2020

Unit tests are great... when they work dependably! In fact, there's an old saying that "a bad test is worse than no test at all." I can attest that...

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Eli Tamošauskas • Jun 28 '22 • Edited

Loving every bit of this! Thanks Dan!

Dan Greene • Jun 30 '22

Thanks you so much for the positive energy. It certainly has been a pattern that has worked well for the teams at our company in the time since we adopted the pattern.

Armando Cifuentes González • May 31 '23 • Edited

Just for curiosity.- To avoid this error Type 'string | undefined' is not assignable to type 'string'. Type 'undefined' is not assignable to type 'string'., without using your library, can I solve it by adding the ! at the end of the property I want to use (I mean, something like this: const field: string = faker().field!;)?

Dan Greene • Jul 8 '23

To avoid that error you have to check to see that the variable is not undefined.

if(yourVariable === undefined){
  throw new Error (“an error message explaining why this is happening”);
}

Armando Cifuentes González • Sep 11 '23

Ok!

Ben Mitchinson • Oct 20 '20

Great write up, thanks for taking the time to describe the issue. Just ran into similar issues, and this provides clear fixes + is a great reference for my team.

Dan Greene • Oct 20 '20

Thank you kindly Ben. And please ask them to share with others. I’d like to see this become a standard within the TS Cypress community.

Again, it’s so generous of you to say thank you. Isn’t dev.to such a wonderful community? :)

Josh Schneider • Jan 10 '23

Very nice article, @dan

All they were thinking about is that they need to test a feature that involves a deleted user. So they add deleted: false to the generalUser object.

Is this supposed to read "So they add deleted: true..." or am I confused?

Chim • Sep 18 '20

🔥🔥🔥

Marijana Rukavina • Sep 6 '21

Thanks Dan for writing this article. It sounds like a direction I would like to go to. I have one question though. How would you solve for Typescript the fact that cypress ui tests need to run on different environments? Meaning you would have to create/load test data objects with different values for different environments. I would appreciate if you could share your thoughts about it. Thanks 😊

Dan Greene • Oct 26 '21

My apologies for not seeing this question sooner. So I would first ask thy you would need different data for mocked tests. Generally mocked tests are designed to test the "shape" of your data, not necessarily real data. As where end-to-end (e2e) tests would rely on both the shape and the content of the data and would therefore not utilize mock data (or factories) at all.

But if you still choose to mock different data per environment, I would consider simply clarifying that in your tests.

let user: IUser | null = null;
if(process.env.NODE_ENV === 'production'){
  user = makeFakeUser({userName: 'John'});
} else if(process.env.NODE_ENV === 'staging'){
  user = makeFakeUser({userName: 'Susan'});
}
// Assert so that the user variable can no longer be seen as null
if(!user){
  throw new Error(`unable to initialize mock user since NODE_ENV was invalid`);
}
// the rest of your test