diff --git a/EclipsingBinaries/tests/test_OC_plot.py b/EclipsingBinaries/tests/test_OC_plot.py
new file mode 100644
index 0000000..47ac703
--- /dev/null
+++ b/EclipsingBinaries/tests/test_OC_plot.py
@@ -0,0 +1,25 @@
+from .OC_plot import calculate_oc
+
+
+def test_calculate_oc():
+    # Test case 1: Test when T0 = 0
+    m = 10.0
+    err = 0.1
+    T0 = 0
+    T0_err = 0.1
+    p = 1.0
+    e, OC, OC_err, T0, T0_err = calculate_oc(m, err, T0, T0_err, p)
+    assert e == 10.0
+    assert OC == "0.00000"
+    assert OC_err == "0.14142"
+
+    # Test case 2: Test when T0 != 0
+    m = 15.0
+    err = 0.1
+    T0 = 5.0
+    T0_err = 0.1
+    p = 2.0
+    e, OC, OC_err, T0, T0_err = calculate_oc(m, err, T0, T0_err, p)
+    assert e == 5.0
+    assert OC == "0.00000"
+    assert OC_err == "0.14142"