Test a balance conversion moving both sides exactly

Failure modes in this flow

The only honest test of a conversion is arithmetic performed against the balances before and after, which is why the first and last steps mirror each other.

Both movements have to match the quoted figures exactly. A conversion that debits $100.00 and credits 91.99 euros displays a correct rate and keeps a cent, which is a rounding bug that only an assertion on the resulting balance will find.

Writing the objective

The rate and the resulting amount are asserted before the conversion is performed, so the figures the customer agreed to are recorded independently of what the conversion then does.

---
mode: testing
url: https://my-testing-repo-main.vercel.app/wise-clone-app/balances?reset=true
max_steps: 40
tags: [wise, payments, balances]
---

# Wize 15.4: Balance conversion

Catalog objective: convert between two balances at the shown rate.
Key assertion: the balances update by exactly the converted amounts.

## Verify the starting balances
Verify "Your balances" shows "USD" of "$2,480.40" and "EUR" of "€310.00".

## Set the conversion up
Leave "From" on "USD" and "To" on "EUR", replace "Amount" with "100", and verify "Rate" reads "1 USD = 0.92 EUR" and "You'll get" reads "€92.00".

## Convert
Click "Convert" and verify a green banner titled "Conversion complete" says "$100.00" was converted to "€92.00" at 1 USD = 0.92 EUR.

## Verify the balances moved by exactly those amounts
Verify "USD" now reads "$2,380.40" and "EUR" now reads "€402.00".

The confirmation banner is asserted with the rate included, which means a conversion executed at a different rate than the one quoted fails at that step rather than being inferred later from the balances.

The assertions in detail

A baseline, a quote, an action, and a verification of both accounts.

Three places to catch a discrepancy: the quote, the confirmation and the balances. A conversion bug that survives all three is not a display problem.

Running it locally

kane-cli testmd run tests/wise/balance-conversion_test.md

This file pins a fixed rate against seeded data. Against a live environment, capture the quoted rate as a variable and assert the balances against that captured value.

Storing a value mid-run and asserting against it later is the pattern for anything rate-dependent. The test.md format covers variables, and evidence based QA covers retaining proof for a balance-moving operation.