MOB-418: on-device self-test (MobWake.SelfTest)

[GenericJam]

Part of MOB-418 / epic MOB-410 (mob_ci nightly e2e).

Native call proving init

MobWake.SelfTest.run/1 makes one read-only call: :mob_wake_nif.platform_signal/0. No UI, nothing scheduled, no state left behind.

Platform	Native path	Answer	Result
iOS	ObjC NIF reads UIApplication.backgroundRefreshStatus (main thread)	%{background_refresh_status: :available | :denied | :restricted}	:pass (denied/restricted are the user's/MDM setting)
Android	Zig NIF → JNI → MobWakeBridge.platformSignal()	%{battery_optimized: bool, has_context: true}	:pass (bridge registered + app context set)
Android	same	%{battery_optimized: bool, has_context: false}	{:fail, "MobWakeBridge has no app context …"}
Android	NIF, register() never ran / method-ID lookup failed	{:error, :bridge_not_registered}	{:fail, …}
Android	NIF, no JNIEnv	{:error, :no_jni_env}	{:fail, …}
host	.erl stub	nif_not_loaded raised	{:fail, "mob_wake_nif is not linked …"}
any	other shape (empty map, other platform's map, …)		{:fail, …}

No skip branch: nothing here needs hardware or the user.

Native fix (Android)

platform_signal/0 used to return %{} when the bridge wasn't registered or no JNIEnv was available — the same answer as a host without the NIF, so a broken host looked healthy. It now returns {:error, :bridge_not_registered} / {:error, :no_jni_env} (like the mob_location pilot, GenericJam/mob_location#8). Mob.Wake.status/1 folds those into platform_signal: %{}, so its public contract is unchanged. Compile-checked locally with zig build-obj -target aarch64-linux-android against mob 0.9.15's mob_erts.zig / mob_zig.zig.

Other

• manifest: selftest: MobWake.SelfTest, mob_version: "~> 0.9"
• mix.exs: {:mob, "~> 0.9 and >= 0.9.15"}, {:mob_dev, "~> 0.7.17", …}; mix.lock updated
• tests: classifier classify/2 covers every branch, each asserted with Mob.Plugin.SelfTest.result?/1; host run/1 hits the stub → fail; manifest declares the self-test with no validator warning. 44 tests, 0 failures; format + credo --strict clean.
• No version bump. Not to be merged until on-device verification (iOS sim + Android emulator).

[GenericJam]

Review: reviewer agent (read-only claude -p, Codex rate-limited until 2026-10-09 02:54): MERGE.

• Pass 1 (f6e5abf): MERGE, with 3 should-fix items: the ErlangError rescue was too broad; the status/1 fold was untested and had no catch-all; the manifest mob_version was coarse. Nitpicks: use erts.errorTuple, document map_build_failed, the bridge_not_registered message.
• Fixes (9852971, e5d4673): catch only :error, :nif_not_loaded; Mob.Wake.normalize_platform_signal/1 (map as-is, anything else → %{}) with its own test; manifest comment says the real floor (>= 0.9.15) is enforced in mix.exs; uses erts.errorTuple; map_build_failed is documented in the NIF comment and the CHANGELOG; the message now names the bootstrap.
• Pass 2 (9852971): MERGE. No regressions. The one remaining nitpick (the CHANGELOG map_build_failed line) is fixed in e5d4673.

CI tests is green on e5d4673 (run 37890356544). Local checks: 45 tests, 0 failures; format and credo --strict are clean; the Android NIF compiles with zig build-obj -target aarch64-linux-android against mob 0.9.15's erts/jni modules. Not merged: waiting for on-device verification.

[GenericJam]

Device verification (MOB-418 group B), blank host mix mob.new st_system --blank --local (mob/mob_dev master = 0.9.15 / 0.7.17), this branch as a path dep, mix mob.deploy --native + mix mob.selftest:

• iOS simulator iPhone 17 (2CAF98B3): pass %{background_refresh_status: :available}
• Android emulator Pixel_8_arm API (emulator-5554): pass %{has_context: true, battery_optimized: true}

Native call: :mob_wake_nif.platform_signal/0 (raw answer shown, captured over rpc on the same deployed app).