Add unit tests for factorial.py (#12815)

* Add unit tests for factorial.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* uvx --python=3.12 unittest2pytest --write test_factorial.py

* Update error message in current_stock_price.py

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>

maths/test_factorial.py

@@ -0,0 +1,37 @@
+# /// script
+# requires-python = ">=3.13"
+# dependencies = [
+#     "pytest",
+# ]
+# ///
+
+import pytest
+
+from maths.factorial import factorial, factorial_recursive
+
+
+@pytest.mark.parametrize("function", [factorial, factorial_recursive])
+def test_zero(function):
+    assert function(0) == 1
+
+
+@pytest.mark.parametrize("function", [factorial, factorial_recursive])
+def test_positive_integers(function):
+    assert function(1) == 1
+    assert function(5) == 120
+    assert function(7) == 5040
+
+
+@pytest.mark.parametrize("function", [factorial, factorial_recursive])
+def test_large_number(function):
+    assert function(10) == 3628800
+
+
+@pytest.mark.parametrize("function", [factorial, factorial_recursive])
+def test_negative_number(function):
+    with pytest.raises(ValueError):
+        function(-3)
+
+
+if __name__ == "__main__":
+    pytest.main(["-v", __file__])