diff --git a/jsprit-core/src/test/java/jsprit/core/problem/solution/route/activity/TimeWindowsImplTest.java b/jsprit-core/src/test/java/jsprit/core/problem/solution/route/activity/TimeWindowsImplTest.java
new file mode 100644
index 00000000..ddf7af60
--- /dev/null
+++ b/jsprit-core/src/test/java/jsprit/core/problem/solution/route/activity/TimeWindowsImplTest.java
@@ -0,0 +1,23 @@
+package jsprit.core.problem.solution.route.activity;
+
+import org.junit.Test;
+
+/**
+ * Created by schroeder on 18/12/15.
+ */
+public class TimeWindowsImplTest {
+
+    @Test(expected = IllegalStateException.class)
+    public void overlappingTW_shouldThrowException(){
+        TimeWindowsImpl tws = new TimeWindowsImpl();
+        tws.add(TimeWindow.newInstance(50, 100));
+        tws.add(TimeWindow.newInstance(90,150));
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void overlappingTW2_shouldThrowException(){
+        TimeWindowsImpl tws = new TimeWindowsImpl();
+        tws.add(TimeWindow.newInstance(50, 100));
+        tws.add(TimeWindow.newInstance(40,150));
+    }
+}