Reinstate "InvokerConcurrencyTest"

Author: RichardBradley

src/test/scala/scoverage/InvokerConcurrencyTest.scala

@@ -0,0 +1,53 @@
+package scoverage
+
+import org.scalatest.FunSuite
+import org.scalatest.BeforeAndAfter
+import java.io.File
+import scala.concurrent._
+import scala.concurrent.duration._
+import ExecutionContext.Implicits.global
+import scala.collection.breakOut
+
+/**
+ * Verify that [[Invoker.invoked()]] is thread-safe
+ */
+class InvokerConcurrencyTest extends FunSuite with BeforeAndAfter {
+
+  val measurementDir = new File("invoker-test.measurement")
+
+  before {
+    deleteMeasurementFiles()
+    measurementDir.mkdirs()
+  }
+
+  test("calling Invoker.invoked on multiple threads does not corrupt the measurement file") {
+
+    val testIds: Set[Int] = (1 to 1000).toSet
+
+    // Create 1k "invoked" calls on the common thread pool, to stress test
+    // the method
+    val futures: List[Future[Unit]] = testIds.map { i: Int =>
+      future {
+        Invoker.invoked(i, measurementDir.toString)
+      }
+    }(breakOut)
+
+    futures.foreach(Await.result(_, 1.second))
+
+    // Now verify that the measurement file is not corrupted by loading it
+    val measurementFiles = IOUtils.findMeasurementFiles(measurementDir)
+    val idsFromFile = IOUtils.invoked(measurementFiles).toSet
+
+    idsFromFile === testIds
+  }
+
+  after {
+    deleteMeasurementFiles()
+    measurementDir.delete()
+  }
+
+  private def deleteMeasurementFiles(): Unit = {
+    if (measurementDir.isDirectory)
+      measurementDir.listFiles().foreach(_.delete())
+  }
+}