I'm interested how to find the location of a screenshot which is created during UI Tests of my app. I would like to understand how Fastlane Snapshot grabs this screenshot. After couple of hours of research I can't find location of those screenshots.
Screenshots are stored inside your Derived Data folder. You can find this by going to Xcode, Window > Projects and click the little arrow next to your derived data path for the project.
From your project derived data folder (should be the name of your folder with a load of letters after it), go to Logs/Test.
Inside the Test folder will be test summary .plist files with UUIDs in their names (one per test run) and a folder called Attachments - the screenshots are in here.
If any of these folders aren't there, make sure you've run the tests first.
To work out which screenshot you want, you'll need to dig through the *_TestSummaries.plist file. Open it in Xcode and follow the test summary down to the SubActivity you're interested in. Some SubActivities don't have screenshots, and will have the HasScreenshotData key set to NO.
When you find a SubActivity with screenshot data, match the UUID for that SubActivity with the filename of the screenshot in the Attachments folder.
My screenshots were located at: /Users/{username}/Library/Developer/Xcode/DerivedData/{project_name}-tywebfjsswmghapfjfbzhuazjf/Logs/Test/Attachments.
In the .plist, I followed this path to find details of the screenshot data for an event: TestableSummaries > Item 0 > Tests > Item 0 > Subtests > Item 0 > Subtests > Item 0 > ActivitySummaries > Item 1 > SubActivities > Item 0.