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Skills migrate-to-shoehorn

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.

install
source · Clone the upstream repo
git clone https://github.com/mattpocock/skills
Claude Code · Install into ~/.claude/skills/
T=$(mktemp -d) && git clone --depth=1 https://github.com/mattpocock/skills "$T" && mkdir -p ~/.claude/skills && cp -r "$T/migrate-to-shoehorn" ~/.claude/skills/mattpocock-skills-migrate-to-shoehorn && rm -rf "$T"
manifest: migrate-to-shoehorn/SKILL.md
source content

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

npm i @total-typescript/shoehorn

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
  });
});

After:

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

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


as Type
→ 
fromPartial()

Before:

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

After:

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

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


as unknown as Type
→ 
fromAny()

Before:

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

After:

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

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

When to use each

FunctionUse 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