Migrate To Shoehorn

by mattpocockc55ee46073edNo licenseListed Oct 8, 2026Updated Oct 8, 2026

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.

Instructions onlySoftware Development

AI-generated overview

Migrates TypeScript test files from as type assertions to the @total-typescript/shoehorn helpers fromPartial, fromAny and fromExact.

What it does: This skill guides an agent through replacing as type assertions in TypeScript test files with helpers from the @total-typescript/shoehorn package. It explains the mapping of as Type to fromPartial(), as unknown as Type to fromAny(), and when to use fromExact(), with before-and-after code examples. It also provides a workflow covering installation, locating test files with assertions, applying replacements, adding imports and running a type check. It is intended for test code only, not production code.
When to use it: Use it when a user mentions shoehorn, wants to remove as assertions from tests, or needs to pass partial or intentionally wrong test data while keeping TypeScript satisfied. It fits TypeScript projects whose test files rely on type assertions for large objects.
Requirements: Requires a TypeScript project with test files and the ability to install the npm package @total-typescript/shoehorn; the workflow uses grep and a type check. It ships no scripts and contains instructions only.

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

Migration patterns

Large objects with few needed properties

Before:

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  });});

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:

import { fromPartial } from "@total-typescript/shoehorn";
it("gets user by id", () => {  getUser(    fromPartial({      body: { id: "123" },    }),  );});

import { fromPartial } from "@total-typescript/shoehorn";
it("gets user by id", () => {  getUser(    fromPartial({      body: { id: "123" },    }),  );});

`as Type` → `fromPartial()`

Before:

After:

import { fromPartial } from "@total-typescript/shoehorn";
getUser(fromPartial({ body: { id: "123" } }));

import { fromPartial } from "@total-typescript/shoehorn";
getUser(fromPartial({ body: { id: "123" } }));

`as unknown as Type` → `fromAny()`

Before:

After:

When to use each

Workflow

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?
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

Source and attribution

Source:mattpocock/skillsinskills/misc/migrate-to-shoehornat commitc55ee46

License: No license

Content belongs to its original authors. SourceWeft indexes it from a public repository.

Report or request removal

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)

Migrate To Shoehorn

Migrate to Shoehorn

Why shoehorn?

Install

Migration patterns

Large objects with few needed properties

`as Type` → `fromPartial()`

`as unknown as Type` → `fromAny()`

When to use each

Workflow

Source and attribution

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Migrate To Shoehorn

Migrate to Shoehorn

Why shoehorn?

Install

Migration patterns

Large objects with few needed properties

as Type → fromPartial()

as unknown as Type → fromAny()

When to use each

Workflow

Source and attribution

More from mattpocock/skills

Chief Of Staff

Writing For Agents

Wait What

To Questionnaire

Teach

Handoff

More in Software Development

Playground

M5 Onboard

Cardputer Buddy

Dpop Adoption

Gemini Live Api

Gemini Api

`as Type` → `fromPartial()`

`as unknown as Type` → `fromAny()`