migrate-to-shoehorn

name	migrate-to-shoehorn
description	Convert `as` type assertions in test files to @total-typescript/shoehorn helpers. Use when the user mentions shoehorn, wants to remove `as` from tests, or needs to pass partial data to a typed function under test.

Migrate to shoehorn

Why shoehorn

shoehorn (published as @total-typescript/shoehorn) lets a test hand a function partial data without the compiler complaining. It swaps casts for helpers that stay type-checked, so the test still fails when the real shape drifts.

Tests only. Keep shoehorn out of production code.

What as costs you in tests:

• It defeats the compiler you are trying to lean on
• You restate the target type by hand at every call site
• Deliberately wrong fixtures need the double cast as unknown as Type

Install

npm i @total-typescript/shoehorn

Migration patterns

A large object where the test needs a couple of fields

Before:

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

it("gets user by id", () => {
  // The test only reads body.id, yet has to fabricate a whole 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 becomes fromPartial()

Before:

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

After:

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

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

as unknown as Type becomes 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 } }));

Which helper to reach for

Function	Use case
fromPartial()	Supply partial data that still type-checks
fromAny()	Supply deliberately wrong data (autocomplete stays)
fromExact()	Require the full object (swap for fromPartial later)

Workflow

1. Scope the change — ask the user:

   • Which test files carry the problematic as assertions?
   • Are these large objects where the test reads only a few fields?
   • Do any tests intentionally pass malformed data to exercise error paths?

2. Install, then migrate:

   • Install: npm i @total-typescript/shoehorn
   • Locate the casts: grep -r " as [A-Z]" --include="*.test.ts" --include="*.spec.ts"
   • Turn as Type into fromPartial()
   • Turn as unknown as Type into fromAny()
   • Import the helpers from @total-typescript/shoehorn
   • Run the type checker to confirm the tests still compile