Reorganise test setup and add additional tests

- Now testing against several Gradle versions (building against latest)
- Using JUnit 5 and Spock 2
- Several test run for both the old method to address Jars (Jar file
  name) and the new method (group:name coordinates)

Author: jjohannes

build.gradle.kts

@@ -16,20 +16,11 @@ java {
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
 }
-val functionalTest: SourceSet by sourceSets.creating
-gradlePlugin.testSourceSets(functionalTest)
-val functionalTestTask = tasks.register<Test>("functionalTest") {
-    group = "verification"
-    testClassesDirs = functionalTest.output.classesDirs
-    classpath = functionalTest.runtimeClasspath
-}
-tasks.check {
-    dependsOn(functionalTestTask)
-}
 
 dependencies {
     implementation("org.ow2.asm:asm:8.0.1")
-    "functionalTestImplementation"("org.spockframework:spock-core:1.2-groovy-2.5")
+
+    testImplementation("org.spockframework:spock-core:2.1-groovy-3.0")
 }
 
 gradlePlugin {
@@ -48,3 +39,23 @@ pluginBundle {
     vcsUrl = "https://github.com/jjohannes/extra-java-module-info.git"
     tags = listOf("java", "modularity", "jigsaw", "jpms")
 }
+
+tasks.test {
+    description = "Runs tests against the Gradle version the plugin is built with"
+    classpath = sourceSets.test.get().runtimeClasspath
+    useJUnitPlatform()
+}
+
+listOf("6.4.1", "6.9.2", "7.0.2").forEach { gradleVersionUnderTest ->
+    val testGradle = tasks.register<Test>("testGradle$gradleVersionUnderTest") {
+        group = "verification"
+        description = "Runs tests against Gradle $gradleVersionUnderTest"
+        testClassesDirs = sourceSets.test.get().output.classesDirs
+        classpath = sourceSets.test.get().runtimeClasspath
+        useJUnitPlatform()
+        systemProperty("gradleVersionUnderTest", gradleVersionUnderTest)
+    }
+    tasks.check {
+        dependsOn(testGradle)
+    }
+}

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.4.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.4.2-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists