migrate-to-shoehorn

What it does

migrate-to-shoehorn rewrites as type assertions in test files into calls to @total-typescript/shoehorn: fromPartial() in place of as Type, and fromAny() in place of the double-assertion as unknown as Type.

The problem it's solving is specific to tests, not code generally. A test that needs a Request object but only cares about body.id still has to satisfy TypeScript for all twenty of that type's other properties if it builds the object with as. shoehorn lets the test supply only what it uses and keeps the rest type-checked as "don't know, don't care" instead of faked.

This is a test-only tool. Nothing here recommends using fromPartial or fromAny in production code, and the skill doesn't touch non-test files.

When to reach for it

Type /migrate-to-shoehorn, or mention wanting to replace as in tests, or needing partial test data, and the agent will reach for it.

Your situation	Fits?
Test files building large fake objects just to satisfy a type, using only a few fields	Yes
Test intentionally passes wrong-shaped data to check error handling, via as unknown as Type	Yes
Assertions in production code	No, out of scope by design
A type genuinely needs to be exact in a test (no partial allowed)	Use fromExact() once installed, not a reason to skip this skill

The two replacements

Before	After	Why
{ body: { id: '123' } } as Request	fromPartial({ body: { id: '123' } })	Only the fields you set are checked; the rest type-check as unknown rather than being faked
{ body: { id: 123 } } as unknown as Request	fromAny({ body: { id: 123 } })	Keeps autocomplete while deliberately passing the wrong shape, for testing how the code handles bad input

A third function, fromExact(), exists for the opposite case: forcing a full object where you'd otherwise reach for fromPartial(), useful if you want a test to fail loudly the moment a new required field appears.

Workflow

1. Ask what test files have as assertions causing friction, whether they're mostly the "large object, few fields matter" shape or the "intentionally wrong data" shape, or both.
2. Install: npm i @total-typescript/shoehorn (adjust for your package manager).
3. Find candidates: grep -r " as [A-Z]" --include="*.test.ts" --include="*.spec.ts".
4. Replace as Type with fromPartial(), and as unknown as Type with fromAny(), adding the import as each file needs it.
5. Run the type checker to confirm nothing regressed.

Common questions

Why not just use Partial<Request> as the parameter type instead? That changes the production function's signature to accept partial input everywhere, which is a much bigger and riskier change than the test needs. shoehorn keeps the real type in the signature and only relaxes what the test has to supply.

Does this change runtime behavior? No. fromPartial and fromAny are identity functions at runtime; they exist purely to change what TypeScript will accept at the call site. If a test passes today, it still passes after the migration, and if it fails, that's an existing test problem the migration exposed rather than introduced.

What if a test is deliberately checking a "wrong type" error path with as unknown as Type? That's exactly the fromAny() case; the intent is preserved, you just keep the editor's autocomplete on the object literal instead of losing it inside a double assertion.

It's working if

• Test files that used to fake unrelated properties now only specify the ones the test actually reads.
• No as Type or as unknown as Type remains in the migrated files, and no such assertion crept into a non-test file as a side effect.
• The type checker passes after the migration with no changes to production signatures.
• Tests that were checking bad-input handling still check the same bad input, just through fromAny() instead of a double assertion.

Where it fits

A narrow, standalone cleanup you run against test files whenever as friction shows up; nothing else in this collection depends on it and it depends on nothing else. It's a natural companion to any TDD-flavored skill in this collection, since tests that construct partial fixtures are exactly what those skills produce.