Improve Mocking Documentation to include detox build

[abury]

Description

Hey Detox Team. 👋

We've been trying to get mocking working for our CI and are running into a lot of issues. We've spent an inordinate amount of time trying to find a way to get detox build working with the RN_SRC_EXT=e2e.js prefix, but we haven't had any luck. Only RN_SRC_EXT=e2e.js react-native start seems to work, however, we can't really do this in a CI setting.

I'm sure there is a simple step missing here. There are a number of Stack Overflow questions (with no or self-answers) on this topic. I think it would be really beneficial for there to be a simple example of how to use mocking alongside the recommended detox build command, or what to use instead.

Thanks! 👍

[LeoNatan]

detox build is a convenience that calls a command provided by you. Why not use RN_SRC_EXT=e2e.js xcodebuild …?

[abury]

Hey @LeoNatan

Thanks for the reply. We've tried using xcodebuild (after clearing ios/build) like so :
RN_SRC_EXT=e2e.js xcodebuild -workspace ios/MyApp.xcworkspace -scheme MyApp -configuration Debug -sdk iphonesimulator -derivedDataPath ios/build

However, this hasn't worked. The only way I can get it to work is by calling
RN_SRC_EXT=e2e.js react-native start
And then manually calling detox test in a separate terminal window.

Is there a different way I should be calling xcodebuild, or perhaps detox build? We already have it set up in detox configuration in our package.json. Is there anything else we need to do?

Thanks! 👍

[LeoNatan]

Which configuration are you running? Release should work.
If Debug, try perhaps starting the packager with that environment variable, and once the packager is running, build with xcodebuild.

[abury]

@LeoNatan Ah, interesting. I believe it is debug, which could explain why it's only working when we start the packager manually. I'll see how we go with a release configuration.

[LeoNatan]

It is always best to test with release configuration as it’s the closest to what users get.

You can also try exporting the env var, which May also help for debug.

[abury]

@LeoNatan That was it! Turns out it needed we needed to be building it as a release configuration. Thanks so much for helping us through that.
It might be worth including in the Advanced Stubbing documentation that it must run on a release configuration to work. I'm more than happy to write that up if you feel it would help 👍

[LeoNatan]

You closed the issue, but I had a follow up question. If you export the env var, does it work for debug?
If so, that might be all that is needed to change in the docs.

[abury]

Hey @LeoNatan. Sorry, I didn't hear back and didn't want to leave tickets open.
I didn't end up needing to try that as we just went with the release configuration. I'm not on this project for another few days but I'll give it a go when I get a chance.