test: set the test Main dispatcher before every spec callback by Lemkinator · Pull Request #256 · Lemkinator/OneUI-Sample-App

Lemkinator · 2026-09-27T21:34:09Z

Summary

Replaces TestDispatcherListener with MainDispatcherExtension, a project TestCaseExtension registered in ProjectConfig. Kotest 6.2.5 runs a spec's beforeContainer/beforeEach callbacks before a project listener's beforeTest. The old listener therefore set Dispatchers.Main too late.
A ViewModel built in beforeEach found no Main when it touched viewModelScope. Lifecycle then falls back to Dispatchers.Default, so its launches raced the test. SettingsViewModelTest's ViewModel now runs on the test thread instead of DefaultDispatcher-worker-2, with no spec edit.
The extension sets Main before a top-level test's callbacks and resets it after that test. Nested tests and after-callbacks keep Main.
AboutViewModelTest, AppPickerViewModelTest, SwitchBarViewModelTest and OOBEViewModelTest drop their own setMain/resetMain.
OOBEViewModelTest names the Main scheduler it advances and builds it in beforeEach. A dispatcher built in the spec body gets its own scheduler, so the ViewModel's delay never advances and the test times out.

Behavior changes

None in app code. This PR changes test infrastructure only.

Coverage

MainDispatcherExtensionTest covers beforeEach, beforeContainer, afterContainer, a nested test, and a Main installed in a container body. Its afterSpec asserts that Main is reset.
The test fails on the old listener.
Kover stays at 100/100.

Verification

spotlessCheck detekt lintDebug testDebugUnitTest koverVerifyDebug verifyRoborazziDebug: PASS, 535 tests.
Full suite: 3 runs green.
Parity: EXACT, drift 0.

Notes

Spec-body initializers, beforeSpec and afterSpec run outside any TestCaseExtension. The extension KDoc states this limit.
Commits:
- 38b5371 test: set the test Main dispatcher before spec callbacks
- 5604a93 test: rely on the project Main dispatcher in ViewModel specs
- 987389f test: name the Main scheduler in the OOBE spec

🤖 Generated with Claude Code

https://claude.ai/code/session_01UXgoU8egK3DzNLho2znqJz

Replace TestDispatcherListener with a project-wide MainDispatcherExtension that sets Dispatchers.Main for root tests and resets it after execution. Add lifecycle and nested-test coverage. Remove redundant per-test Main dispatcher setup from four ViewModel test suites.

Kotest runs spec beforeEach and beforeContainer callbacks before a BeforeTestListener, so a ViewModel built there found no Main and its viewModelScope fell back to Dispatchers.Default. A TestCaseExtension wraps every callback of a top-level test; it resets Main only after that test, so nested tests and after-callbacks still see the dispatcher.

MainDispatcherExtension now sets Main before beforeEach, so the specs drop their own setMain and resetMain. The OOBE spec builds its dispatcher in beforeEach: a TestDispatcher created there shares the scheduler of the test Main, while one created in the spec body gets its own scheduler and no longer advances the ViewModel's delay.

The spec holds the scheduler of the test Main dispatcher, taken in beforeEach, and advances it directly, so the dependency on Main's scheduler shows in the code.

coderabbitai · 2026-09-27T21:34:22Z

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Advanced

Run ID: 61d51993-958b-4760-9ab6-3bcb26b0c83b

📥 Commits

Reviewing files that changed from the base of the PR and between c5228ec and 987389f.

📒 Files selected for processing (7)

app/src/test/java/de/lemke/oneuisample/MainDispatcherExtension.kt
app/src/test/java/de/lemke/oneuisample/MainDispatcherExtensionTest.kt
app/src/test/java/de/lemke/oneuisample/ui/AboutViewModelTest.kt
app/src/test/java/de/lemke/oneuisample/ui/AppPickerViewModelTest.kt
app/src/test/java/de/lemke/oneuisample/ui/OOBEViewModelTest.kt
app/src/test/java/de/lemke/oneuisample/ui/SwitchBarViewModelTest.kt
app/src/test/java/io/kotest/provided/ProjectConfig.kt

💤 Files with no reviewable changes (3)

app/src/test/java/de/lemke/oneuisample/ui/AppPickerViewModelTest.kt
app/src/test/java/de/lemke/oneuisample/ui/SwitchBarViewModelTest.kt
app/src/test/java/de/lemke/oneuisample/ui/AboutViewModelTest.kt

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📝 Walkthrough

Walkthrough

The test suite replaces its per-test Main dispatcher listener with a Kotest test-case extension. New tests cover dispatcher behavior across test lifecycles, and ViewModel tests remove local Main dispatcher setup.

Changes

Main dispatcher test setup

Layer / File(s)	Summary
Add and register the dispatcher extension `app/src/test/java/de/lemke/oneuisample/MainDispatcherExtension.kt`, `app/src/test/java/io/kotest/provided/ProjectConfig.kt`, `app/src/test/java/de/lemke/oneuisample/MainDispatcherExtensionTest.kt`	A `TestCaseExtension` installs an `UnconfinedTestDispatcher` for root tests and resets `Main` afterward. `ProjectConfig` registers the extension. New tests check dispatcher behavior across test and container lifecycles.
Update ViewModel test dispatcher setup `app/src/test/java/de/lemke/oneuisample/ui/AboutViewModelTest.kt`, `app/src/test/java/de/lemke/oneuisample/ui/AppPickerViewModelTest.kt`, `app/src/test/java/de/lemke/oneuisample/ui/OOBEViewModelTest.kt`, `app/src/test/java/de/lemke/oneuisample/ui/SwitchBarViewModelTest.kt`	ViewModel tests remove per-test `Main` replacement and reset. The OOBE navigation test advances a stored `TestCoroutineScheduler`.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Other

Merge Risk: ⚪ Minimal · up to 98738

The shared dispatcher setup covers nested ViewModel tests, with no identified issue requiring a fix before merge.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 98738

The change is confined to test infrastructure, and no new application attack path was identified. The remaining risk is that overlapping tests could interfere with each other’s dispatcher state; whether such overlap occurs is not established.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

inferred — Any dispatcher-isolation failure identified here would affect JVM test execution rather than directly grant an application privilege or expose a deployed service.

Trust Boundaries and Controls

observed — The regression test expects Main during test callbacks and expects it to be unavailable in afterSpec; the extension does not promise Main for the spec lifecycle outside intercepted test cases.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 4 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: configuring the test Main dispatcher before spec callbacks. It is concise and directly related to the changeset.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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_{A rabbit checks the dispatcher’s pace,
Then hops through each test-case place.
Main returns when root tests end,
A scheduler helps events ascend.
The burrow’s tests now run in line.}

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mergestorm-vortex · 2026-09-27T21:34:25Z

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greptile-apps · 2026-09-27T21:37:23Z

Confidence Score: 5/5

[Low risk] Test infrastructure refactors dispatcher setup.

The PR appears safe to merge; no actionable regression was identified.

Summary

The PR moves test Main-dispatcher setup from a listener to a root-test extension, removes redundant ViewModel-spec setup, and adds lifecycle coverage.

The OOBE test now captures the Main scheduler during beforeEach for its delayed-event assertion.

_{Reviews (1) · Last reviewed commit: "test: name the Main scheduler in the OOB..."}

codecov · 2026-09-27T21:41:15Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

📢 Thoughts on this report? Let us know!

Lemkinator added 3 commits September 27, 2026 22:58

test: name the Main scheduler in the OOBE spec

987389f

The spec holds the scheduler of the test Main dispatcher, taken in beforeEach, and advances it directly, so the dependency on Main's scheduler shows in the code.

Lemkinator merged commit 10b692d into main Sep 29, 2026
10 checks passed

Lemkinator deleted the test/main-dispatcher-extension branch September 29, 2026 16:15

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test: set the test Main dispatcher before every spec callback - #256

test: set the test Main dispatcher before every spec callback#256
Lemkinator merged 3 commits into
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test/main-dispatcher-extension

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Summary

Behavior changes

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Confidence Score: 5/5

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Lemkinator commented Sep 27, 2026 •

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