diff --git a/.github/workflows/python-tests.yaml b/.github/workflows/python-tests.yaml
new file mode 100644
index 0000000..37fe76d
--- /dev/null
+++ b/.github/workflows/python-tests.yaml
@@ -0,0 +1,26 @@
+name: Python package
+
+on: [push]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.8", "3.10"]
+
+    steps:
+      - uses: actions/checkout@v3
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v4
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Install dependencies
+        # This case we are only updating pip, but you could add other dependencies needed.
+        run: |
+          python3 -m pip install --upgrade pip
+          python3 -m pip install pytest
+      - name: Test with pytest
+        run: |
+          python3 -m pytest
diff --git a/test_times.py b/test_times.py
new file mode 100644
index 0000000..6dc8205
--- /dev/null
+++ b/test_times.py
@@ -0,0 +1,60 @@
+import times
+from times import time_range
+from times import compute_overlap_time
+#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))
+
+def test_given_input():
+    intervals1 =  time_range("2010-01-12 10:00:00", "2010-01-12 12:00:00")
+    intervals2 =  time_range("2010-01-12 10:30:00", "2010-01-12 10:45:00", 2, 60)
+
+    result = compute_overlap_time(intervals1, intervals2)
+    print('Result: ', result)
+    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')]
+    print('Expected: ', expected)
+    assert result == expected
+
+
+def test_no_overlap():
+
+    intervals1 =  time_range("2010-01-12 10:00:00", "2010-01-12 12:00:00")
+    intervals2 =  time_range("2010-01-12 16:00:00", "2010-01-12 19:00:00", 2, 60*60)
+
+    result = compute_overlap_time(intervals1, intervals2)
+    print('Result: ', result)
+    expected = []
+    print('Expected: ', expected)
+    assert result == expected
+'''
+def test_multiple_ranges():
+
+    intervals1 =  time_range("2010-01-12 10:00:00", "2010-01-12 13:00:00", 2, 3600)
+    intervals2 =  time_range("2010-01-12 11:00:00", "2010-01-12 14:00:00", 2, 60*60)
+
+    result = compute_overlap_time(intervals1, intervals2)
+    print('Result: ', result)
+    expected = [('2010-01-12 11:00:00', '2010-01-12 11:00:00'), \
+                ('2010-01-12 12:00:00', '2010-01-12 12:00:00')]
+    print('Expected: ', expected)
+    assert result == expected
+'''
+'''
+def test_same_time():
+    
+    intervals1 =  time_range("2010-01-12 10:00:00", "2010-01-12 12:00:00")
+    intervals2 =  time_range("2010-01-12 09:00:00", "2010-01-12 12:00:00", 2, 60*60)
+
+    result = compute_overlap_time(intervals1, intervals2)
+    print('Result: ', result)
+    expected = [("2010-01-12 10:00:00", "2010-01-12 10:00:00"),\
+                ("2010-01-12 11:00:00", "2010-01-12 12:00:00")]
+    print('Expected: ', expected)
+    assert result == expected
+
+'''
+'''
+def test_interval():
+    wrong_interval = time_range("2010-01-12 12:00:00", "2010-01-12 10:00:00")
+'''
diff --git a/times.py b/times.py
index d57f401..2d8aa61 100644
--- a/times.py
+++ b/times.py
@@ -1,9 +1,12 @@
 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")
+
+    if (start_time_s > end_time_s):
+        raise ValueError('Interval cannot start with a time later than the end time.')
+
     d = (end_time_s - start_time_s).total_seconds() / number_of_intervals + gap_between_intervals_s * (1 / number_of_intervals - 1)
     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))
@@ -23,4 +26,6 @@ def compute_overlap_time(range1, range2):
 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))
+
+