NowChessSystems/docs/superpowers/specs/2026-03-22-scalatest-scoverage-design.md

Design: Add ScalaTest + Replace JaCoCo with Scoverage

Date: 2026-03-22 Status: Approved

Summary

Replace the current JUnit-only test setup and JaCoCo coverage with ScalaTest (via its JUnit 5 bridge) and Scoverage across both modules/core and modules/api.

Motivation

• The CLAUDE.md working agreement prescribes AnyFunSuite with Matchers with JUnitSuiteLike as the unit test style, which requires ScalaTest.
• Scoverage is the standard Scala code coverage tool and understands Scala semantics; JaCoCo's JVM bytecode instrumentation is less accurate for Scala code.

Scope

Two modules are affected: modules/core and modules/api. The root build.gradle.kts is updated for shared dependency versions only.

Changes

Root build.gradle.kts

Add to the versions map (dependency versions only — plugin version is hardcoded per module, see note below):

• SCALATEST → 3.2.19
• SCALATESTPLUS_JUNIT5 → 3.2.19.1

Note on plugin versioning: Gradle resolves the plugins {} block before rootProject.extra is available, so the Scoverage plugin version (8.1) must be declared inline in each module's plugins {} block. It cannot be read from the root versions map.

modules/core/build.gradle.kts and modules/api/build.gradle.kts

Both modules require the same set of changes. Both currently have two separate tasks.test {} blocks that must be merged into one.

Plugins block:

• Remove jacoco
• Add id("org.scoverage") version "8.1"

Dependencies block:

• Remove testImplementation(platform("org.junit:junit-bom:5.10.0"))
• Remove testImplementation("org.junit.jupiter:junit-jupiter")
• Remove testRuntimeOnly("org.junit.platform:junit-platform-launcher")
• Add testImplementation("org.scalatest:scalatest_3:${versions["SCALATEST"]!!}")
• Add testImplementation("org.scalatestplus:junit-5-11_3:${versions["SCALATESTPLUS_JUNIT5"]!!}")

Task wiring — merge both tasks.test {} blocks into one and replace jacoco wiring:

Both modules/core and modules/api currently have two tasks.test {} blocks. Delete both and replace with the following single merged block placed after the dependencies {} block (conventional position):

tasks.test {
    useJUnitPlatform()   // required — scalatestplus JUnit 5 bridge relies on this
    finalizedBy(tasks.reportScoverage)
}
tasks.reportScoverage {
    dependsOn(tasks.test)
}

Note: modules/api does not currently have useJUnitPlatform() — it must be added (not just kept) in the merged block.

Remove the jacocoTestReport task block entirely from both modules.

Task name confirmation: The Scoverage Gradle plugin 8.1 registers reportScoverage as the HTML report task.

Versions

Artifact	Version	Notes
org.scalatest:scalatest_3	3.2.19	Core ScalaTest for Scala 3
org.scalatestplus:junit-5-11_3	3.2.19.1	JUnit 5.11 runner bridge; .1 = build 1
Scoverage Gradle plugin	8.1	Hardcoded inline in plugins {} block

Testing the Change

After applying:

1. ./gradlew :modules:core:test and ./gradlew :modules:api:test must pass (green, even with zero test files).
2. ./gradlew :modules:core:reportScoverage must produce a coverage report.
3. ./gradlew build must be fully green.

Files Modified

• build.gradle.kts (root) — add two version entries
• modules/core/build.gradle.kts — plugin, deps, merge two tasks.test blocks, replace jacoco wiring
• modules/api/build.gradle.kts — plugin, deps, merge two tasks.test blocks, add useJUnitPlatform(), replace jacoco wiring

No new source files are created.