jakkaj

---
name: eng-harness-in-a-box
description: |
  The engineering-harness loop with zero dependencies — an engineering harness in a box.
  Use in any repo, especially one with no harness yet: find or establish a
  focal operating surface, name the deterministic proof before working,
  capture friction as you go, and offer one encodable improvement at the end.
  Advisory always — the user is never blocked, the agent is never silent.
  When a repo has an installed harness CLI and wants the full loop, use
  eng-harness-flow instead.

jakkaj

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>pij — the deterministic layer</title>
<style>
  :root{
    --paper:#F3F6F4;
    --card:#FFFFFF;

jakkaj

from datetime import datetime

# Test doubles implement the same interfaces as production code
class FakeBookingRepository(BookingRepository):
    """In-memory repository for testing - no HTTP, no database."""
    def __init__(self):
        self._bookings: dict[str, Booking] = {}

    def find_by_id(self, booking_id: BookingId) -> Booking | None:
        return self._bookings.get(booking_id.value)

jakkaj

# Interface lives in the application/domain module
from abc import ABC, abstractmethod
from typing import Optional
import httpx

class BookingRepository(ABC):
    @abstractmethod
    async def find_by_id(self, booking_id: BookingId) -> Optional["Booking"]:
        pass

jakkaj

from dataclasses import dataclass
from datetime import datetime
from abc import ABC, abstractmethod

# Domain command + IDs used at the boundary of the application layer
@dataclass
class BookingId:
    value: str

@dataclass

jakkaj

from datetime import datetime

# Test doubles implement the same interfaces as production code
class FakeBookingRepository(BookingRepository):
    """In-memory repository for testing - no HTTP, no database."""
    def __init__(self):
        self._bookings: dict[str, Booking] = {}

    def find_by_id(self, booking_id: BookingId) -> Booking | None:
        return self._bookings.get(booking_id.value)

jakkaj

jakkaj

jakkaj

# Interface visible to application services
from abc import ABC, abstractmethod
from dataclasses import dataclass

class PaymentAdapter(ABC):
    @abstractmethod
    async def charge(self, request: "PaymentRequest") -> "PaymentResult":
        pass

# Domain-facing request/result types

jakkaj

# Interface lives in the application/domain module
from abc import ABC, abstractmethod
from typing import Optional
import httpx

class BookingRepository(ABC):
    @abstractmethod
    async def find_by_id(self, booking_id: BookingId) -> Optional["Booking"]:
        pass