Fix local E2E selection on Bash 3.2

[kieran-osgood-shopify]

TLDR

Fix local E2E test selection under macOS Bash 3.2 by avoiding empty-array expansion with set -u.

This addresses the positional-file and tag-only failures reported after #705 merged.

What changed

• Guard de-duplication when no test files have been selected yet.
• Guard positional test resolution when a run only uses tags.
• Exercise positional and tag-only selection through the system Bash.

How to test

GIVEN a Mac whose /bin/bash --version reports Bash 3.2 and a booted iOS simulator

WHEN the reviewer runs /bin/bash ./e2e/scripts/run_local_e2e swift-ios tests/shared/launch-smoke.yaml

THEN the Swift sample should build and the Launch smoke flow should pass instead of exiting with RESOLVED_TEST_FILES[@]: unbound variable

---

GIVEN a Mac whose /bin/bash --version reports Bash 3.2 and a booted iOS simulator

WHEN the reviewer runs /bin/bash ./e2e/scripts/run_local_e2e swift-ios --tags smoke

THEN all enabled Swift smoke flows should pass instead of exiting while expanding an empty test-file array

[bitrise]

Install this build

Open Tophat, select your target device, then click Install. Links open on the Mac running Tophat.

SDK	Install
React Native	Install with Tophat
Swift	Install with Tophat
Kotlin	Install with Tophat

Checkout Kit E2E results

Status	Suite	Target	Platform	OS version tag	Device
✅	react-native-ios	react-native	ios	latest	iPhone 15 iOS 27 Beta
✅	react-native-android	react-native	android	latest	Google Pixel 9 Android 17.0
❌	kotlin-android	kotlin	android	latest	Google Pixel 9 Android 17.0
✅	swift-ios	swift	ios	latest	iPhone 15 iOS 27 Beta

Failures

Caution

These E2E checks are not yet required, so they do not block merging — but a failure may still indicate a real issue to resolve before merging.
If you believe an assertion is flaky, please raise a ticket in the #checkout-kit-devs channel so it can be addressed.

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Android — kotlin-android

Test	Status	Artifacts
—	❌	BrowserStack