Migrate To Shoehorn

Migrate to Shoehorn

Why shoehorn?

shoehorn 让你在 tests 中传入 partial data，同时让 TypeScript 保持满意。它用 type-safe alternatives 替换 as assertions。

Test code only. 永远不要在 production code 中使用 shoehorn。

Tests 中 as 的问题：

• 被训练成不使用它
• 必须手动指定 target type
• 对 intentionally wrong data 需要 double-as（as unknown as Type）

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

Workflow

1. Gather requirements - 询问用户：

   • 哪些 test files 有造成问题的 as assertions？
   • 它们是否在处理 large objects，而只有部分 properties 重要？
   • 是否需要为 error testing 传入 intentionally wrong data？

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