Test propagation across non-tracing contexts

dd-java-agent-ittests/src/main/scala/datadog/trace/agent/integration/executors/ScalaConcurrentTests.scala

@@ -32,6 +32,22 @@ class ScalaConcurrentTests {
     return 5
   }
 
+  @Trace
+  def tracedAcrossThreadsWithNoTrace() :Integer = {
+    val goodFuture: Future[Integer] = Future {
+      1
+    }
+    goodFuture onSuccess {
+      case _ => Future {
+        2
+      } onSuccess {
+        case _ => tracedChild("callback")
+      }
+    }
+
+    return 2
+  }
+
   /**
     * @return Number of expected spans in the trace
     */

dd-java-agent-ittests/src/test/groovy/datadog/trace/agent/integration/executors/ExecutorInstrumentationTest.groovy

@@ -136,6 +136,17 @@ class ExecutorInstrumentationTest extends Specification {
     trace.size() == expectedNumberOfSpans
   }
 
+  def "scala propagates across futures with no traces"() {
+    setup:
+    ScalaConcurrentTests scalaTest = new ScalaConcurrentTests()
+    int expectedNumberOfSpans = scalaTest.tracedAcrossThreadsWithNoTrace()
+    testWriter.waitForTraces(1)
+    List<DDSpan> trace = testWriter.get(0)
+
+    expect:
+    trace.size() == expectedNumberOfSpans
+  }
+
   def "scala either promise completion"() {
     setup:
     ScalaConcurrentTests scalaTest = new ScalaConcurrentTests()