test: add us-cpa module coverage and citations

skills/us-cpa/tests/test_tax_years.py

@@ -0,0 +1,25 @@
+from __future__ import annotations
+
+import unittest
+
+from us_cpa.tax_years import supported_tax_years, tax_year_rules
+
+
+class TaxYearRuleTests(unittest.TestCase):
+    def test_supported_years_are_listed(self) -> None:
+        self.assertEqual(supported_tax_years(), [2024, 2025])
+
+    def test_tax_year_rules_include_source_citations(self) -> None:
+        rules = tax_year_rules(2025)
+
+        self.assertIn("sourceCitations", rules)
+        self.assertIn("standardDeduction", rules["sourceCitations"])
+        self.assertIn("ordinaryIncomeBrackets", rules["sourceCitations"])
+
+    def test_unsupported_tax_year_raises_clear_error(self) -> None:
+        with self.assertRaisesRegex(ValueError, "Unsupported tax year 2023"):
+            tax_year_rules(2023)
+
+
+if __name__ == "__main__":
+    unittest.main()