I noticed two XCTests tests that are not running because their return types are not the expected void (fixed in flutter/engine#51983):

- (bool)testSetWarnsOnOverflow

https://github.com/flutter/engine/blob/76a270f6cc31ba3e83cc602f983eb2302dbbe1e8/shell/platform/darwin/common/framework/Source/FlutterChannelsTest.m#L171

- (bool)testNextResponderShouldThrowOnPressesEnded

https://github.com/flutter/engine/blob/76a270f6cc31ba3e83cc602f983eb2302dbbe1e8/shell/platform/darwin/ios/framework/Source/FlutterKeyboardManagerTest.mm#L151

https://developer.apple.com/documentation/xctest/defining_test_cases_and_test_methods?language=objc

Add some kind of lint or tooling check to the engine to detect this case.