Checklist

• I've run bundle exec rspec from the root directory to see all new and existing tests pass
• I've followed the fastlane code style and run bundle exec rubocop -a to ensure the code style is valid
• I see several green ci/circleci builds in the "All checks have passed" section of my PR (connect CircleCI to GitHub if not)
• I've read the Contribution Guidelines
• I've updated the documentation if necessary.
• I've added or updated relevant unit tests.

Motivation and Context

snapshot already prepares simulators by resolving a concrete simulator UDID. For example, it opens Simulator and runs simctl commands against that UDID:

open -a Simulator.app --args -CurrentDeviceUDID F24194FE-5DD3-470D-991D-6A91C456657A
xcrun simctl uninstall F24194FE-5DD3-470D-991D-6A91C456657A com.techprimate.Flinky

But the generated xcodebuild command did not use that same UDID. It emitted a separate platform,name,OS destination:

xcodebuild \
  -scheme ScreenshotUITests \
  -project ./Flinky.xcodeproj \
  -configuration Debug \
  -destination 'platform=iOS Simulator,name=iPhone 17 Pro,OS=26.4' \
  FASTLANE_SNAPSHOT=YES \
  FASTLANE_LANGUAGE=en-US \
  build test

That can fail when CoreSimulator and xcodebuild disagree about the string OS version for the same simulator runtime. In the observed CI failure, snapshot prepared an iPhone 17 Pro simulator by UDID, but xcodebuild failed to resolve OS=26.4:

xcodebuild: error: Unable to find a device matching the provided destination specifier:
		{ platform:iOS Simulator, OS:26.4, name:iPhone 17 Pro }

The requested device could not be found because no available devices matched the request.

The available destinations in that job included iPhone 17 Pro devices for OS:26.4.1 and OS:26.5, but not OS:26.4.

CI references:

• Failing screenshot job: https://github.com/techprimate/Flinky/actions/runs/26625119973/job/78459945916
• Working screenshot job using this fork branch: https://github.com/techprimate/Flinky/actions/runs/26628467999/job/78470982015?pr=129

Description

This changes the modern snapshot test command generator to pass the resolved simulator UDID to xcodebuild:

-destination 'platform=iOS Simulator,id=<resolved simulator UDID>'

The important part is that xcodebuild now receives the same simulator identity that snapshot uses during simulator preparation. This avoids a second destination lookup by name and OS, which can select no device or a different device when runtime metadata is inconsistent.

The local reproduction environment had both iOS 26.4 and iOS 26.4.1 runtimes installed. simctl list runtimes reported both under the same display runtime name and identifier:

iOS 26.4 (26.4 - 23E244) - com.apple.CoreSimulator.SimRuntime.iOS-26-4
iOS 26.4 (26.4.1 - 23E254a) - com.apple.CoreSimulator.SimRuntime.iOS-26-4

simctl list devices then printed duplicate -- iOS 26.4 -- sections, while xcodebuild -showdestinations reported the same simulator UDID as OS:26.4.1:

{ platform:iOS Simulator, arch:arm64, id:B49A866F-9928-4BE5-B64C-43057EB05198, OS:26.4.1, name:iPhone 17 Pro }

Using a UDID destination avoids depending on the mismatched OS string.

This also keeps explicit ios_version behavior: if a user configures ios_version, snapshot still uses that version when resolving the simulator. The change removes the implicit LatestOsVersion.version(os) lookup from the default destination path so the generated xcodebuild command uses the same default simulator lookup contract as the preparation steps. Without that, snapshot could still prepare one UDID and run tests on another one.

The older Xcode 8 generator already used a UDID destination. This aligns the modern generator with that approach.

Regression coverage was added for:

• generated destinations using id=<udid> instead of name=<name>,OS=<version>;
• the generated xcodebuild destination matching TestCommandGenerator.device_udid;
• iOS, tvOS, and watchOS command expectations using UDID destinations.

Testing Steps

Focused destination regression specs:

bundle exec rspec \
  snapshot/spec/test_command_generator_spec.rb:31 \
  snapshot/spec/test_command_generator_spec.rb:42 \
  snapshot/spec/test_command_generator_spec.rb:52

Broader command-generator specs:

bundle exec rspec \
  snapshot/spec/test_command_generator_spec.rb \
  snapshot/spec/test_command_generator_xcode_8_spec.rb

Manual destination reproduction:

xcodebuild -showBuildSettings \
  -scheme ScreenshotUITests \
  -project ./Flinky.xcodeproj \
  -configuration Debug \
  -destination 'platform=iOS Simulator,name=iPhone 17 Pro,OS=26.4'

Observed result:

xcodebuild: error: Could not configure request to show build settings: Unable to find a device matching the provided destination specifier:
		{ platform:iOS Simulator, OS:26.4, name:iPhone 17 Pro }

The same request succeeds when addressed by concrete UDID:

xcodebuild -showBuildSettings \
  -scheme ScreenshotUITests \
  -project ./Flinky.xcodeproj \
  -configuration Debug \
  -destination 'platform=iOS Simulator,id=FC42BA48-38ED-4A94-8E96-5512C25BB0F9'

Observed result includes:

TARGET_DEVICE_IDENTIFIER = FC42BA48-38ED-4A94-8E96-5512C25BB0F9
TARGET_DEVICE_OS_VERSION = 26.5

fixes: #29553
fixes: #29481
fixes: #30040
fixes: #22284