For testing use

```typescript
import {tap, expect} @push.rocks/tapbundle
```

tapbundle exports expect from @push.rocks/smartexpect
You can find the readme here: https://code.foss.global/push.rocks/smartexpect/src/branch/master/readme.md

This module also uses @tsclass/tsclass: You can find the TInvoice type here: https://code.foss.global/tsclass/tsclass/src/branch/master/ts/finance/invoice.ts

Don't use shortcuts when doing things, e.g. creating sample data in order to not implement something correctly, or skipping tests, and calling it a day.

It is ok to ask questions, if you are unsure about something.