[E2E] Prove ready preload cache hits on both native samples by kyle-schellen · Pull Request #627 · Shopify/checkout-kit

kyle-schellen · 2026-08-11T15:10:45Z

What changed

Proves that presentation actually reused the preloaded WebView, and exposes that proof to Maestro on both native samples.

Swift SDK: emit a debug-only diagnostic through the configured Logger when presentation selects a matching cached WebView that reached .ready. The existing OSLog message is preserved for dashboard compatibility.
Swift sample: observe that diagnostic as it is written and republish it as an invisible preload-cache-hit-* identifier. Normal launches hide the diagnostic marker from the accessibility tree; [E2E] Prepare native preload ready-flow validation #631 enables preload observability only for diagnostic runs.
Android SDK/sample: keep the existing cache-hit log behavior, pin its exact internal diagnostic in an SDK test, and read the app's PID-scoped Logcat. Each watcher writes a unique UUID boundary after its reader starts, ignores every line until that boundary appears, and then republishes the cache-hit identifier only when the latest observed preload state is Ready. The debug-only watcher owns and closes its reader/process with the CartViewModel.
Tests cover ready hits, still-loading entries, non-debug logging, fresh presentation, URL mismatch, exact diagnostic strings, stale hits before the current UUID boundary, old UUID sessions, Android Ready gating, Logcat failures, and reader/process shutdown.

Why

preload-state-ready proves background preload completed. It does not prove presentation used that cached WebView — a fresh one looks identical on screen. This closes that gap.

The .ready condition matters: a cached entry that matches but is still loading would otherwise count as a hit.

Both samples end up exposing the same identifier, so the E2E flow has no platform branch. Getting there differs only because the SDKs differ:

	How the sample sees the cache hit
Swift	Installs a `Logger`, so it observes the message directly
Kotlin	SDK log sink is `internal`, so it reads its own PID-scoped Logcat. A per-watcher UUID boundary excludes buffered lines from earlier app processes before the observer accepts a cache hit

Each sample matches the message text against its own copy because the SDK diagnostics are not public API. SDK emission tests and sample parser tests pin the exact literals, so accidental drift fails close to the change instead of surfacing as a 30-second E2E timeout.

Testing

dev swift test CheckoutWebViewTests
dev swift test sample
dev android test demo, dev android check detekt
PreloadCacheHitMarkerTest: stale pre-boundary hits, old UUID sessions, current-boundary arming, Ready gating, Logcat failures, and reader shutdown
dev swift lint
dev android e2e --tags preload
dev swift e2e --tags preload
Asserted end to end by [E2E] Prepare native preload ready-flow validation #631 on both platforms: preload ready → present → real checkout content → close → preload-cache-hit-observed, with preload-cache-hit-none asserted beforehand so a stuck marker cannot pass.

Stack

[E2E] Expose native preload state markers #626 — preload state markers in the samples
[E2E] Prove ready preload cache hits on both native samples #627 — this PR: proof that the ready cache entry was reused
[E2E] Prepare native preload ready-flow validation #631 — the E2E test and matrix wiring

Before you merge

Important

I've added tests to support my implementation
I have read and agree with the Contribution Guidelines
I have read and agree with the Code of Conduct
I've updated the relevant platform README (platforms/swift/README.md and/or platforms/android/README.md)

Releasing a new Swift version?

I have bumped the version in ShopifyCheckoutKit.podspec
I have bumped the version in platforms/swift/Sources/ShopifyCheckoutKit/ShopifyCheckoutKit.swift
I have updated the SwiftPM/CocoaPods version snippets in platforms/swift/README.md (major version only)

Releasing a new Embedded Checkout Protocol version?

I have bumped embeddedCheckoutProtocolAndroid in platforms/android/gradle/libs.versions.toml
I have updated protocol/languages/kotlin/embedded-checkout-protocol/api/embedded-checkout-protocol.api if the public API changed

Releasing a new Android version?

I have bumped checkoutKitAndroid in platforms/android/gradle/libs.versions.toml
I have updated the Gradle/Maven version snippets in platforms/android/README.md

Tip

See the Contributing documentation for the full release process per platform.

kyle-schellen · 2026-08-11T15:11:00Z

This stack of pull requests is managed by Graphite. Learn more about stacking.

bitrise · 2026-08-11T22:44:19Z

Install this build

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

SDK	Install
Swift	Install with Tophat
Kotlin	Install with Tophat

Checkout Kit E2E results

Status	Suite	Target	Platform	OS version tag	Device
✅	`kotlin-android`	kotlin	android	latest	Google Pixel 11 Android 17.0
✅	`swift-ios`	swift	ios	latest	iPhone 15 iOS 27 Beta

kieran-osgood-shopify · 2026-08-12T12:30:47Z

Dropping it here based on our slack convo
We're going to explore an approach using the log screen as this avoids us having to add conditional logs entries to the SDK

github-actions · 2026-08-19T23:12:02Z

Package Size

Platform	Artifact	Base	Head	Delta
Android	release AAR	291.2 KiB	291.3 KiB	+170 B

Android file breakdown

File	Base	Head	Delta
`classes.jar`	308.4 KiB	308.5 KiB	+152 B
`res/layout/checkout_view_content.xml`	2.6 KiB	2.6 KiB	0 B
`res/layout/checkout_sheet_content.xml`	2.0 KiB	2.0 KiB	0 B
`res/values/values.xml`	1.3 KiB	1.3 KiB	0 B
`R.txt`	1.2 KiB	1.2 KiB	0 B
`AndroidManifest.xml`	922 B	922 B	0 B
`proguard.txt`	798 B	798 B	0 B
`res/drawable/close.xml`	431 B	431 B	0 B
`res/menu/checkout_menu.xml`	354 B	354 B	0 B
`META-INF/com/android/build/gradle/aar-metadata.properties`	157 B	157 B	0 B

Measured from the PR base SHA and PR head SHA. The file breakdown shows uncompressed sizes within each package artifact, so individual files do not sum to the compressed artifact total. This comment reports package artifact sizes only; it is not a final app binary-size report.

kieran-osgood-shopify · 2026-08-21T10:03:58Z

+class PreloadCacheHitLog(
+    private val openLines: () -> LogStream = ::followOwnLogcat,
+    private val isPreloadReady: () -> Boolean = { false },
+    private val reportError: (Throwable) -> Unit = {
+        Timber.e(it, "Failed to observe the preload cache-hit diagnostic")
+    },
+) {
+    companion object {
+        /** Must stay in step with PreloadCache.kt, which logs this on a cache hit. */
+        const val DIAGNOSTIC = "Returning cached preloaded WebView."
+
+        /** Starts at the newest entry so earlier runs cannot create a false hit. */
+        private fun followOwnLogcat(): LogStream {
+            val process = ProcessBuilder(
+                "logcat", "-T", "1", "--pid=${Process.myPid()}", "PreloadCache:D", "*:S"
+            ).redirectErrorStream(true).start()
+            val reader = BufferedReader(InputStreamReader(process.inputStream))
+
+            return LogStream(reader.lineSequence()) {
+                process.destroy()
+                runCatching { reader.close() }
+            }
+        }
+    }


Have you been able to do much testing against this to ensure it doesn't false positive?
I'm wondering if at app launch we can add a marker UUID that designates the start of logs to read from to avoid possible conflicts reading a stale cache hit marker

## What changed - Observe `PreloadState` in the Swift and Android sample apps using the existing public preload callbacks. - Expose the readiness result through matching invisible test IDs on both platforms: - `preload-state-not-ready` - `preload-state-ready` - Add unit tests for the shared readiness-to-ID contract. ## Why Maestro cannot read an in-memory Swift/Kotlin preload state. These markers give native E2E tests a stable condition to wait for before presentation. The identifier changes to `preload-state-ready` only when the SDK callback reports `Ready`, so the test does not infer preload completion from timing. The markers add no visible UI and no public SDK API. ## Testing - `dev swift test sample` - `dev android test demo` - `dev swift lint` - `dev android check detekt` - Consumed by the preload E2E test in #631, green on physical iOS and Android devices. ## Stack 1. **#626 — this PR:** preload state markers in the samples 2. #627 — ready cache-hit proof and sample markers 3. #631 — the E2E test, matrix wiring, and BrowserStack validation --- ### Before you merge > [!IMPORTANT] > - [x] I've added tests to support my implementation > - [x] I have read and agree with the [Contribution Guidelines](./CONTRIBUTING.md) > - [ ] I have read and agree with the [Code of Conduct](./CODE_OF_CONDUCT.md) > - [ ] I've updated the relevant platform README (`platforms/swift/README.md` and/or `platforms/android/README.md`) --- <details> <summary>Releasing a new Swift version?</summary> - [ ] I have bumped the version in `ShopifyCheckoutKit.podspec` - [ ] I have bumped the version in `platforms/swift/Sources/ShopifyCheckoutKit/ShopifyCheckoutKit.swift` - [ ] I have updated the SwiftPM/CocoaPods version snippets in `platforms/swift/README.md` (major version only) </details> <details> <summary>Releasing a new Embedded Checkout Protocol version?</summary> - [ ] I have bumped `embeddedCheckoutProtocolAndroid` in `platforms/android/gradle/libs.versions.toml` - [ ] I have updated `protocol/languages/kotlin/embedded-checkout-protocol/api/embedded-checkout-protocol.api` if the public API changed </details> <details> <summary>Releasing a new Android version?</summary> - [ ] I have bumped `checkoutKitAndroid` in `platforms/android/gradle/libs.versions.toml` - [ ] I have updated the Gradle/Maven version snippets in `platforms/android/README.md` </details> > [!TIP] > See the [Contributing documentation](./CONTRIBUTING.md) for the full release process per platform.

github-actions Bot added the #gsd:50662 Rebase Checkout Kit on UCP label Aug 11, 2026

kyle-schellen mentioned this pull request Aug 11, 2026

[E2E] Expose native preload state markers #626

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kyle-schellen force-pushed the ks-e2e-preload-cache-hit-signal branch from 9055f4f to bd7199e Compare August 11, 2026 15:16

kyle-schellen changed the title ~~test(e2e): standardize native preload cache-hit signals~~ [E2E] Swift preload cache-hit signal Aug 11, 2026

kyle-schellen force-pushed the ks-e2e-preload-cache-hit-signal branch 2 times, most recently from 7a4eef0 to c408a61 Compare August 11, 2026 19:11

kyle-schellen force-pushed the ks-e2e-preload-sample-markers branch from 558cb61 to 76447c5 Compare August 11, 2026 19:11

kyle-schellen force-pushed the ks-e2e-preload-cache-hit-signal branch 2 times, most recently from e26b2d8 to 67a0382 Compare August 11, 2026 21:48

kyle-schellen self-assigned this Aug 11, 2026

kyle-schellen marked this pull request as ready for review August 11, 2026 22:39

kyle-schellen requested a review from a team as a code owner August 11, 2026 22:39

kyle-schellen force-pushed the ks-e2e-preload-cache-hit-signal branch from 67a0382 to 4a1fa10 Compare August 11, 2026 22:57

kyle-schellen marked this pull request as draft August 12, 2026 12:31

kyle-schellen force-pushed the ks-e2e-preload-cache-hit-signal branch from 4a1fa10 to acd0a6a Compare August 12, 2026 13:45

kyle-schellen changed the title ~~[E2E] Swift preload cache-hit signal~~ [E2E] Log ready Swift preload cache hits Aug 12, 2026

kyle-schellen force-pushed the ks-e2e-preload-sample-markers branch from 76447c5 to 770e7de Compare August 12, 2026 17:58

kyle-schellen force-pushed the ks-e2e-preload-cache-hit-signal branch from acd0a6a to 1842281 Compare August 12, 2026 17:58

kyle-schellen mentioned this pull request Aug 12, 2026

[E2E] Prepare native preload ready-flow validation #631

Open

11 tasks

kyle-schellen force-pushed the ks-e2e-preload-sample-markers branch from 770e7de to 56cc7f5 Compare August 14, 2026 20:36

kyle-schellen force-pushed the ks-e2e-preload-cache-hit-signal branch 3 times, most recently from b8e8758 to 7abc816 Compare August 17, 2026 23:30

kyle-schellen force-pushed the ks-e2e-preload-sample-markers branch from 56cc7f5 to 49478c1 Compare August 17, 2026 23:30

kyle-schellen changed the title ~~[E2E] Log ready Swift preload cache hits~~ [E2E] Prove ready preload cache hits on both native samples Aug 17, 2026

kyle-schellen force-pushed the ks-e2e-preload-sample-markers branch from 49478c1 to 715c1f5 Compare August 18, 2026 13:30

kyle-schellen force-pushed the ks-e2e-preload-cache-hit-signal branch from 7abc816 to d973bac Compare August 18, 2026 13:30

kyle-schellen force-pushed the ks-e2e-preload-cache-hit-signal branch 4 times, most recently from a747354 to fbeab52 Compare August 19, 2026 22:29

kyle-schellen marked this pull request as ready for review August 19, 2026 23:09

kyle-schellen force-pushed the ks-e2e-preload-cache-hit-signal branch from fbeab52 to d737760 Compare August 19, 2026 23:26

kieran-osgood-shopify reviewed Aug 21, 2026

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kyle-schellen force-pushed the ks-e2e-preload-cache-hit-signal branch from d737760 to 4f03d86 Compare August 21, 2026 13:51

kyle-schellen changed the base branch from ks-e2e-preload-sample-markers to graphite-base/627 August 21, 2026 16:22

kyle-schellen force-pushed the ks-e2e-preload-cache-hit-signal branch from 4f03d86 to a331852 Compare August 21, 2026 16:22

kyle-schellen force-pushed the graphite-base/627 branch from 715c1f5 to 25f45e0 Compare August 21, 2026 16:22

kyle-schellen changed the base branch from graphite-base/627 to ks-e2e-preload-sample-markers August 21, 2026 16:22

kyle-schellen changed the base branch from ks-e2e-preload-sample-markers to graphite-base/627 August 21, 2026 19:22

kyle-schellen force-pushed the ks-e2e-preload-cache-hit-signal branch from a331852 to 3b0adea Compare August 21, 2026 19:22

kyle-schellen force-pushed the graphite-base/627 branch from 25f45e0 to 0fdad6c Compare August 21, 2026 19:22

graphite-app Bot changed the base branch from graphite-base/627 to main August 21, 2026 19:23

test(e2e): surface the Swift preload cache-hit signal

f5937d8

kyle-schellen force-pushed the ks-e2e-preload-cache-hit-signal branch from 3b0adea to f5937d8 Compare August 21, 2026 19:23

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