migrate-to-shoehorn✓ Pass

SKILL.md Content

---
name: migrate-to-shoehorn
description: Migrate test files from `as` type assertions to @total-typescript/shoehorn. Use when user mentions shoehorn, wants to replace `as` in tests, or needs partial test data.
---

# Migrate to Shoehorn

## Why shoehorn?

`shoehorn` lets you pass partial data in tests while keeping TypeScript happy. It replaces `as` assertions with type-safe alternatives.

**Test code only.** Never use shoehorn in production code.

Problems with `as` in tests:

- Trained not to use it
- Must manually specify target type
- Double-as (`as unknown as Type`) for intentionally wrong data

## Install

```bash
npm i @total-typescript/shoehorn
```

## Migration patterns

### Large objects with few needed properties

Before:

```ts
type Request = {
  body: { id: string };
  headers: Record<string, string>;
  cookies: Record<string, string>;
  // ...20 more properties
};

it("gets user by id", () => {
  // Only care about body.id but must fake entire Request
  getUser({
    body: { id: "123" },
    headers: {},
    cookies: {},
    // ...fake all 20 properties
  });
});
```

After:

```ts
import { fromPartial } from "@total-typescript/shoehorn";

it("gets user by id", () => {
  getUser(
    fromPartial({
      body: { id: "123" },
    }),
  );
});
```

### `as Type` → `fromPartial()`

Before:

```ts
getUser({ body: { id: "123" } } as Request);
```

After:

```ts
import { fromPartial } from "@total-typescript/shoehorn";

getUser(fromPartial({ body: { id: "123" } }));
```

### `as unknown as Type` → `fromAny()`

Before:

```ts
getUser({ body: { id: 123 } } as unknown as Request); // wrong type on purpose
```

After:

```ts
import { fromAny } from "@total-typescript/shoehorn";

getUser(fromAny({ body: { id: 123 } }));
```

## When to use each

| Function        | Use case                                           |
| --------------- | -------------------------------------------------- |
| `fromPartial()` | Pass partial data that still type-checks           |
| `fromAny()`     | Pass intentionally wrong data (keeps autocomplete) |
| `fromExact()`   | Force full object (swap with fromPartial later)    |

## Workflow

1. **Gather requirements** - ask user:
   - What test files have `as` assertions causing problems?
   - Are they dealing with large objects where only some properties matter?
   - Do they need to pass intentionally wrong data for error testing?

2. **Install and migrate**:
   - [ ] Install: `npm i @total-typescript/shoehorn`
   - [ ] Find test files with `as` assertions: `grep -r " as [A-Z]" --include="*.test.ts" --include="*.spec.ts"`
   - [ ] Replace `as Type` with `fromPartial()`
   - [ ] Replace `as unknown as Type` with `fromAny()`
   - [ ] Add imports from `@total-typescript/shoehorn`
   - [ ] Run type check to verify

License

Declared license: MIT

MIT License

Copyright (c) 2026 amazingloft999-droid

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
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copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

View the license in the source repository — the version published there is authoritative.