diff --git a/testing/src/main/scala/sbt/TestReportListener.scala b/testing/src/main/scala/sbt/TestReportListener.scala
index 2e1f517a6..056e57c47 100644
--- a/testing/src/main/scala/sbt/TestReportListener.scala
+++ b/testing/src/main/scala/sbt/TestReportListener.scala
@@ -10,22 +10,27 @@ import sbt.util.{ Level, Logger }
 
 trait TestReportListener {
   /** called for each class or equivalent grouping */
-  def startGroup(name: String)
+  def startGroup(name: String): Unit
+
   /** called for each test method or equivalent */
-  def testEvent(event: TestEvent)
+  def testEvent(event: TestEvent): Unit
+
   /** called if there was an error during test */
-  def endGroup(name: String, t: Throwable)
+  def endGroup(name: String, t: Throwable): Unit
+
   /** called if test completed */
-  def endGroup(name: String, result: TestResult.Value)
+  def endGroup(name: String, result: TestResult.Value): Unit
+
   /** Used by the test framework for logging test results*/
   def contentLogger(test: TestDefinition): Option[ContentLogger] = None
 }
 
 trait TestsListener extends TestReportListener {
   /** called once, at beginning. */
-  def doInit()
+  def doInit(): Unit
+
   /** called once, at end. */
-  def doComplete(finalResult: TestResult.Value)
+  def doComplete(finalResult: TestResult.Value): Unit
 }
 
 /** Provides the overall `result` of a group of tests (a suite) and test counts for each result type. */
diff --git a/testing/src/main/scala/sbt/TestStatusReporter.scala b/testing/src/main/scala/sbt/TestStatusReporter.scala
index 45f267035..18571227b 100644
--- a/testing/src/main/scala/sbt/TestStatusReporter.scala
+++ b/testing/src/main/scala/sbt/TestStatusReporter.scala
@@ -12,7 +12,7 @@ import scala.collection.mutable.Map
 private[sbt] class TestStatusReporter(f: File) extends TestsListener {
   private lazy val succeeded = TestStatus.read(f)
 
-  def doInit {}
+  def doInit = ()
   def startGroup(name: String): Unit = { succeeded remove name }
   def testEvent(event: TestEvent): Unit = ()
   def endGroup(name: String, t: Throwable): Unit = ()