What changed

The kmp-module convention plugin never configured a test framework for the KMP JVM target, so jvmTest ran without the JUnit Platform and silently discovered zero JUnit 5/Kotest tests in every KMP module (logging, logging-testlib, otel-backend, tests/fixtures). The task passed in ~1 s producing no test reports.

• buildSrc/src/main/kotlin/kmp-module.gradle.kts — the tasks block now configures named<Test>("jvmTest") with useJUnitPlatform() and configureLogging(), mirroring what module-testing.setupTests() does for the test task of a jvm-module. Deliberate divergences (documented in the KDoc): module-testing itself cannot be applied to a KMP module (it brings java-library, which conflicts with kotlin("multiplatform")), and no includeEngines("junit-jupiter") filter is imposed because kmp-module adds the Kotest runner — a separate JUnit Platform engine — to jvmTest dependencies.
• backends/otel-backend/build.gradle.kts — removes the module-local workaround that is now redundant.
• .agents/tasks/kmp-jvmtest-junit-platform.md — task record with verification evidence and the triage log.

The buildSrc change anticipates the identical fix in the config repository (committed there as 512c1068 on the local address-logging-audit-finding branch; it needs its own PR and the usual float — ./config/pull will keep the copies in sync).

Latent failures surfaced and fixed

Enabling the platform revived tests that had silently not run, exposing 25 failures from drift between tests and production code. Production bugs fixed (the tests were right):

• AbstractLogger.atConfig() delegated to Level.INFO instead of Level.CONFIG (now pinned by a regression test covering the whole convenience-method family). The Level class-KDoc "Adding custom levels" example, which used CONFIG as its custom-level illustration, now uses a syslog-style NOTICE instead.
• MetadataHandler.Builder.addRepeatedHandler had inverted validation — it rejected repeatable keys instead of requiring them (drift from Cover custom MetadataKey; align factory parameter naming #144; now covered positively and negatively).
• MetadataKey.cast() returned null instead of the documented ClassCastException; repeated-value guards threw IllegalStateException where IllegalArgumentException is correct.
• SimpleProcessor "wrapped" repeated-value lists with a no-op cast, letting handlers mutate them; replaced with a genuinely unmodifiable iterator.
• ScopedLoggingContext.Builder lacked a member run(Runnable), so Kotlin's stdlib run extension executed blocks without installing the context. The jvmMain call(Runnable) extension it supersedes is now deprecated with a ReplaceWith.
• Lazy log messages were evaluated outside the recursion guard of AbstractLogger.write, letting throwing/reentrant toString() escape error handling; log timestamps lacked milliseconds and UTC offset.

Test expectations were updated where production was right (logger names, synthetic lambda method names, eager rate-limiter counting, Kotlin spread operator for logVarargs).

Verification

• :logging:jvmTest executes 234 tests, all passing (was: zero discovered, then 25 failing when first enabled).
• :otel-backend:jvmTest passes 22/22 without the local workaround; :logging-testlib:jvmTest runs 3 previously-skipped tests.
• Full ./gradlew build dokkaGenerate green; pre-PR gate PASS (reviewers: kotlin-engineer, spine-code-review, review-docs).
• Codecov now receives real coverage from the KMP modules for the first time (base shows 0 because tests never ran on master).

🤖 Generated with Claude Code