diff --git a/test_times.py b/test_times.py
new file mode 100644
index 0000000..35fe83e
--- /dev/null
+++ b/test_times.py
@@ -0,0 +1,19 @@
+
+
+import times
+from times import compute_overlap_time, time_range
+
+def test_given_example():
+    large = time_range("2010-01-12 10:00:00", "2010-01-12 12:00:00")
+    short = time_range("2010-01-12 10:30:00", "2010-01-12 10:45:00", 2, 60)  
+    result = compute_overlap_time(large, short)
+    expected = [('2010-01-12 10:30:00', '2010-01-12 10:37:00'), ('2010-01-12 10:38:00', '2010-01-12 10:45:00')]
+    assert result == expected
+
+def test_do_no_overlap():
+    time1 = time_range("2010-01-12 10:00:00", "2010-01-12 10:30:00")
+    time2 = time_range("2010-01-12 10:45:00", "2010-01-12 11:00:00", 2, 60)  
+    result = compute_overlap_time(time1, time2)
+    expected = []
+    assert result == expected
+
diff --git a/times.py b/times.py
index d57f401..e8910a3 100644
--- a/times.py
+++ b/times.py
@@ -1,6 +1,5 @@
 import datetime
 
-
 def time_range(start_time, end_time, number_of_intervals=1, gap_between_intervals_s=0):
     start_time_s = datetime.datetime.strptime(start_time, "%Y-%m-%d %H:%M:%S")
     end_time_s = datetime.datetime.strptime(end_time, "%Y-%m-%d %H:%M:%S")
@@ -8,6 +7,8 @@ def time_range(start_time, end_time, number_of_intervals=1, gap_between_interval
     sec_range = [(start_time_s + datetime.timedelta(seconds=i * d + i * gap_between_intervals_s),
                   start_time_s + datetime.timedelta(seconds=(i + 1) * d + i * gap_between_intervals_s))
                  for i in range(number_of_intervals)]
+    #print ([(ta.strftime("%Y-%m-%d %H:%M:%S"), tb.strftime("%Y-%m-%d %H:%M:%S")) for ta, tb in sec_range])
+
     return [(ta.strftime("%Y-%m-%d %H:%M:%S"), tb.strftime("%Y-%m-%d %H:%M:%S")) for ta, tb in sec_range]
 
 
@@ -17,10 +18,12 @@ def compute_overlap_time(range1, range2):
         for start2, end2 in range2:
             low = max(start1, start2)
             high = min(end1, end2)
-            overlap_time.append((low, high))
+            #overlap_time.append((low, high))
+            if low < high:
+                overlap_time.append((low, high))
     return overlap_time
 
 if __name__ == "__main__":
     large = time_range("2010-01-12 10:00:00", "2010-01-12 12:00:00")
     short = time_range("2010-01-12 10:30:00", "2010-01-12 10:45:00", 2, 60)
-    print(compute_overlap_time(large, short))
\ No newline at end of file
+    print(compute_overlap_time(large, short))