How to access tests jar in gradle in multi-module project

Question

I have multimodule project. From one of the modules I need to refer the test classes from other module. I tried to configure like this:

// core project
val testJar by tasks.registering(Jar::class) {
    archiveClassifier.set("tests")
    from(project.the<SourceSetContainer>()["test"].output)
}
val testArtifact by configurations.creating
artifacts.add(testArtifact.name, testJar)

And I'm trying to refer to that configuration from other project:

dependencies {
    // other dependencies ommited
    api(project(":core"))
    testImplementation(project(path = ":core", configuration = "testArtifact"))
}

But this configuration doesn't work. The compilation of other project is failing as it doesn't see the required tests classes from core project. The dependency insight:

./gradlew :service:dependencyInsight --dependency core --configuration testCompileClasspath

It gives following:

project :core
  variant "apiElements" [
    org.gradle.usage = java-api
  ]
  variant "testArtifact" [
    Requested attributes not found in the selected variant:
      org.gradle.usage = java-api
  ]

I'm struggling to understand how to make configuration to work so that I can compile the service project's test classes. Running on Gradle 5.2.1 with Kotlin DSL.

Answer 1

So what is described above works on the command line but not in the IDE.

Here is a variation, that builds on the variant-aware dependency management:

plugins {
    `java-library`
}

repositories {
    mavenCentral()
}

group = "org.test"
version = "1.0"

val testJar by tasks.registering(Jar::class) {
    archiveClassifier.set("tests")
    from(project.the<SourceSetContainer>()["test"].output)
}

// Create a configuration for runtime
val testRuntimeElements by configurations.creating {
    isCanBeConsumed = true
    isCanBeResolved = false
    attributes {
        attribute(Usage.USAGE_ATTRIBUTE, project.objects.named(Usage::class, Usage.JAVA_RUNTIME_JARS))
    }
    outgoing {
        // Indicate a different capability (defaults to group:name:version)
        capability("org.test:lib-test:$version")
    }
}

// Second configuration declaration, this is because of the API vs runtime difference Gradle makes and rules around valid multiple variant selection
val testApiElements by configurations.creating {
    isCanBeConsumed = true
    isCanBeResolved = false
    attributes {
        // API instead of runtime usage
        attribute(Usage.USAGE_ATTRIBUTE, project.objects.named(Usage::class, Usage.JAVA_API_JARS))
    }
    outgoing {
        // Same capability
        capability("org.test:lib-test:$version")
    }
}

artifacts.add(testRuntimeElements.name, testJar)
artifacts.add(testApiElements.name, testJar)

Because of the variant-aware dependency management rules, the above looks like a lot. But if it was extracted in a plugin, most of this could be factored out.

And on the consumer side:

testImplementation(project(":lib")) {
    capabilities {
        // Indicate we want a variant with a specific capability
        requireCapability("org.test:lib-test")
    }
}

Note that this requires Gradle 5.3.1. The import of the project in IntelliJ 2019.1 properly wires up the dependencies and test code can compile in the IDE.

Answer 2

Which IDE ? It works for me both in terminal and IDE : I use IntelliJ (2019.3) and Gradle (6.0.1, not Kotlin DSL)