move snapshot tests to separate files

[milahu]

currently we store multiple test cases together

  it("transforms a to b", () => {
    expect(
      t(`
        a
      `)
    ).toBe(
      format(`
        b
      `)
    );
  });
  it("transforms c to d", () => {
    expect(
      t(`
        c
      `)
    ).toBe(
      format(`
        d
      `)
    );
  });

... for example in packages/codemod/test/transforms/replaceReactUseEffect.test.ts

make this more pretty by storing the test cases in separate files
for example in packages/codemod/test/transforms/replaceReactUseEffect/

transforms a to b.src.ts

a

transforms a to b.out.ts

b

make this more pretty

benefit: pretty git diff

similar issue BuilderIO/mitosis#856

compromise solutions with jest-snapshot ...

expect("a").toMatchSnapshot() // snapshot is stored in __snapshots__/*.snap
expect("a").toMatchInlineSnapshot("b")

→ update snapshots with npx jest -u

https://jestjs.io/docs/snapshot-testing