Xcode UI Testing: Automatically taking snapshot when predicates fail?

Question

Xcode UI Testing takes automatic screenshots for viewing in the results navigator whenever a test fails, which is greatly helpful. However, that does not include tests that fail because a predicate is failed. Since predicates are often for basic checks (such as if an element exists or not on a current view), that is a huge drawback because a screenshot would be useful in diagnosing what was happening in the app when the test failed.

Does anyone know how to force a screenshot? Does this require integrating the Fastlane Snapshot tool?

Answer 1

On tearDown you can check if test failed (that's helpful if you are not discarding screenshots when tests pass.)

if let failureCount = testRun?.failureCount, failureCount > 0 {
  takeScreenshot()
}

If you are using Xcode 9 already, the takeScreenshot function can use the new API (If not, then use the workaround mentioned by the other answer) :

let screenshot = XCUIScreen.main.screenshot()
let attach = XCTAttachment(screenshot: screenshot)
add(attach)

You can also name the attach and change its lifetime ;)

See Apple's documentation for how to use and where to find them (the "Report navigator" in View > Navigators > Reports) in more detail.