Use pre-compiled test runner assembly

Dockerfile

@@ -5,7 +5,8 @@ WORKDIR /opt/test-runner
 COPY project/ project/
 COPY src/ src/
 COPY build.sbt build.sbt
-RUN sbt compile
+RUN sbt assembly
+RUN chmod +x target/scala-2.12/TestRunner-assembly-0.1.0-SNAPSHOT.jar
 
 COPY . .
 

bin/run.sh

@@ -54,8 +54,6 @@ mv -f "${original_tests_file}" "${tests_file}"
 popd > /dev/null
 
 # Write the results.json file
-# sbt "set offline := true"
-
-java -jar "target/scala-2.13/TestRunner-assembly-0.1.0-SNAPSHOT.jar ${build_log_file} ${tests_results_file} ${results_file}" > "${runner_log_file}"
+java -jar target/scala-2.12/TestRunner-assembly-0.1.0-SNAPSHOT.jar "${build_log_file}" "${tests_results_file}" "${results_file}" > "${runner_log_file}"
 
 echo "${slug}: done"

build.sbt

@@ -1,6 +1,6 @@
 import Dependencies._
 
-ThisBuild / scalaVersion     := "2.13.5"
+ThisBuild / scalaVersion     := "2.12.8"
 ThisBuild / version          := "0.1.0-SNAPSHOT"
 ThisBuild / organization     := "org.exercism"
 ThisBuild / organizationName := "exercism"

project/Dependencies.scala

@@ -1,5 +1,5 @@
 import sbt._
 
 object Dependencies {
-  lazy val scalaTest = "org.scalatest" %% "scalatest" % "3.0.8"
+  lazy val scalaTest = "org.scalatest" %% "scalatest" % "3.0.1"
 }