Configure parallel tests with Kotlin

The following is sample of a buildspec.yml that shows parallel test execution with Kotlin on an Linux platform:

version: 0.2

batch:
  fast-fail: false
  build-fanout:
    parallelism: 2
    ignore-failure: false

phases:
  install:
    runtime-versions:
      java: corretto11 
    commands:
      - echo 'Installing dependencies'
      - KOTLIN_VERSION="1.8.20" # Replace with your desired version
      - curl -o kotlin-compiler.zip -L "https://github.com/JetBrains/kotlin/releases/download/v${KOTLIN_VERSION}/kotlin-compiler-${KOTLIN_VERSION}.zip"
      - unzip kotlin-compiler.zip -d /usr/local
      - export PATH=$PATH:/usr/local/kotlinc/bin
      - kotlin -version
      - curl -O https://repo1.maven.org/maven2/org/junit/platform/junit-platform-console-standalone/1.8.2/junit-platform-console-standalone-1.8.2.jar
  pre_build:
    commands:
      - echo 'prebuild'
  build:
    commands:
      - echo 'Running Kotlin Tests'
      - |
        codebuild-tests-run \
          --test-command 'kotlinc src/main/kotlin/*.kt $(echo "$CODEBUILD_CURRENT_SHARD_FILES" | tr "\n" " ") -d classes -cp junit-platform-console-standalone-1.8.2.jar' \
          --files-search "codebuild-glob-search 'src/test/kotlin/*.kt'"
      - |
        codebuild-tests-run \
          --test-command '
            java -jar junit-platform-console-standalone-1.8.2.jar --class-path classes \
              $(for file in $CODEBUILD_CURRENT_SHARD_FILES; do
                 class_name=$(basename "$file" .kt)
                 echo "--select-class $class_name"
               done)
          ' \
          --files-search "codebuild-glob-search 'src/test/kotlin/*.kt'"
  post_build:
    commands:
      - echo "Test execution completed"

In the above example, the codebuild-tests-run CLI is used twice. During the first run, kotlinc compiles the files. The CODEBUILD_CURRENT_SHARD_FILES variable retrieves the test files assigned to the current shard, which are then converted into a space-separated list. In the second run, JUnit executes the tests. Again, CODEBUILD_CURRENT_SHARD_FILES fetches the test files assigned to the current shard, but this time they are converted into class names.