From 3d6e0f9327022a661d3236caa74dbd226701467f Mon Sep 17 00:00:00 2001
From: jvican <jorgevc@fastmail.es>
Date: Tue, 2 May 2017 21:10:48 +0200
Subject: [PATCH] Handle empty case in `labelsAndDirs`

---
 .../src/main/scala/sbt/test/ScriptedTests.scala | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/scripted/sbt/src/main/scala/sbt/test/ScriptedTests.scala b/scripted/sbt/src/main/scala/sbt/test/ScriptedTests.scala
index 053466a38..85405e87f 100644
--- a/scripted/sbt/src/main/scala/sbt/test/ScriptedTests.scala
+++ b/scripted/sbt/src/main/scala/sbt/test/ScriptedTests.scala
@@ -96,14 +96,15 @@ final class ScriptedTests(resourceBaseDirectory: File,
         (groupName, testName) -> testDirectory
     }
 
-    val batchSeed = labelsAndDirs.size / sbtInstances
-    val batchSize = if (batchSeed == 0) labelsAndDirs.size else batchSeed
-    labelsAndDirs
-      .grouped(batchSize)
-      .map { batch => () =>
-        IO.withTemporaryDirectory(runBatchedTests(batch, _, prescripted, log))
-      }
-      .toList
+    if (labelsAndDirs.isEmpty) List()
+    else {
+      val batchSeed = labelsAndDirs.size / sbtInstances
+      val batchSize = if (batchSeed == 0) labelsAndDirs.size else batchSeed
+      labelsAndDirs
+        .grouped(batchSize)
+        .map(batch => () => IO.withTemporaryDirectory(runBatchedTests(batch, _, prescripted, log)))
+        .toList
+    }
   }
 
   /** Defines an auto plugin that is injected to sbt between every scripted session.