diff --git a/.github/workflows/python-tests.yml b/.github/workflows/python-tests.yml
new file mode 100644
index 0000000..05e6a49
--- /dev/null
+++ b/.github/workflows/python-tests.yml
@@ -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
+        run: |
+          python -m pip install --upgrade pip
+          python -m pip install pytest
+      - name: Test with pytest
+        run: |
+          pytest 
\ No newline at end of file
diff --git a/__pycache__/test_times.cpython-310-pytest-7.2.0.pyc b/__pycache__/test_times.cpython-310-pytest-7.2.0.pyc
new file mode 100644
index 0000000..e2a9d51
Binary files /dev/null and b/__pycache__/test_times.cpython-310-pytest-7.2.0.pyc differ
diff --git a/__pycache__/times.cpython-310.pyc b/__pycache__/times.cpython-310.pyc
new file mode 100644
index 0000000..8548683
Binary files /dev/null and b/__pycache__/times.cpython-310.pyc differ
diff --git a/test_times.py b/test_times.py
new file mode 100644
index 0000000..7f349c1
--- /dev/null
+++ b/test_times.py
@@ -0,0 +1,36 @@
+from times import compute_overlap_time, time_range
+from pytest import raises
+
+def test_given_input():
+    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_no_overlap():
+    range1 = time_range("2010-01-12 10:00:00", "2010-01-12 12:00:00")
+    range2 = time_range("2010-01-12 13:30:00", "2010-01-12 13:45:00",2, 60)
+    result = compute_overlap_time(range1,range2)
+    expected = [('0000-00-00 00:00:00', '0000-00-00 00:00:00')]
+    assert result == expected
+
+def test_more_intervals():
+    range1 = time_range("2010-01-12 10:00:00", "2010-01-12 12:00:00",4)
+    range2 = time_range("2010-01-12 10:30:00", "2010-01-12 10:45:00",2, 60)
+    result = compute_overlap_time(range1, range2)
+    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_end_start():
+    range1 = time_range("2010-01-12 10:00:00", "2010-01-12 12:00:00")
+    range2 = time_range("2010-01-12 12:00:00", "2010-01-12 13:45:00",2, 60)
+    result = compute_overlap_time(range1, range2)
+    expected = [('0000-00-00 00:00:00', '0000-00-00 00:00:00')]
+    assert result == expected
+
+def test_fails_inverted_interval():
+    with raises(ValueError):
+        range1 = time_range("2010-01-12 11:00:00", "2010-01-12 10:00:00")
+        range2 = time_range("2010-01-12 12:00:00", "2010-01-12 13:45:00",2, 60)
+        compute_overlap_time(range1, range2)
diff --git a/times.py b/times.py
index d57f401..1930bcf 100644
--- a/times.py
+++ b/times.py
@@ -15,12 +15,19 @@ def compute_overlap_time(range1, range2):
     overlap_time = []
     for start1, end1 in range1:
         for start2, end2 in range2:
+            if start1 > end1 or start2 > end2:
+                raise ValueError("Start time should not be after the end time")
             low = max(start1, start2)
             high = min(end1, end2)
-            overlap_time.append((low, high))
+            if low < high:
+                overlap_time.append((low, high))
+    if overlap_time == []:
+        overlap_time = [('0000-00-00 00:00:00', '0000-00-00 00:00:00')]
     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)
+    large = time_range("2010-01-12 10:00:00", "2010-01-12 12:00:00",4)
+    short = time_range("2010-01-12 10:30:00", "2010-01-12 10:45:00",2, 60)
+    print('Large ', large)
+    print('Short', short)
     print(compute_overlap_time(large, short))
\ No newline at end of file