First commit

part1-pricing/tests/test_discounts.py

@@ -0,0 +1,43 @@
+import pytest
+
+from pricing.discounts import apply_discounts
+
+
+def test_no_discounts():
+    assert apply_discounts(100.0, []) == 100.0
+
+
+def test_single_discount():
+    assert apply_discounts(100.0, [25]) == 75.0
+
+
+def test_single_discount_rounding():
+    assert apply_discounts(19.99, [15]) == 16.99
+
+
+def test_stacked_discounts():
+    # two seasonal discounts stacked on one order
+    assert apply_discounts(100.0, [10, 20]) == 70.0
+
+
+def test_stacked_same_discount_twice():
+    assert apply_discounts(100.0, [50, 50]) == 25.0
+
+
+def test_full_discount_is_allowed():
+    assert apply_discounts(80.0, [100]) == 0.0
+
+
+def test_rejects_discount_over_100():
+    with pytest.raises(ValueError):
+        apply_discounts(100.0, [120])
+
+
+def test_rejects_negative_discount():
+    with pytest.raises(ValueError):
+        apply_discounts(100.0, [-5])
+
+
+def test_rejects_negative_base_price():
+    with pytest.raises(ValueError):
+        apply_discounts(-10.0, [10])