generate test on the fly

gentest.ts

import path from 'path'
import fs from 'fs'

const jestSpecTemplate = ({
  moduleName,
  fnName,
  args
}: {
  moduleName: string
  fnName: string
  args: string
}): string => `
import {${fnName}} from './${moduleName}'

test('generated', () => {
  expect(${fnName}(${args})).toMatchInlineSnapshot();
});
`

let c = 0

export const genTest = (fn: any) => {
  const p = new Proxy(fn, {
    apply: function (target, thisArg, argumentsList) {
      console.log('~ argumentsList', argumentsList)
      console.log('~ thisArg', thisArg)
      const returnVal = target.apply(thisArg, argumentsList)
      console.log('~ returnVal', returnVal)
      console.warn('GENTEST-START:')
      const spec = jestSpecTemplate({
        moduleName: path.basename(__filename),
        fnName: fn.name,
        args: argumentsList
          .map((arg) => {
            if (typeof arg === 'object') {
              return JSON.stringify(arg)
            }
            return arg
          })
          .join(', ')
      })
      fs.mkdirSync('./__tests__/generated', { recursive: true })
      fs.writeFileSync(`./__tests__/generated/${fn.name}-${c}.test.ts`, spec)
      console.warn('GENTEST-END:')

      return returnVal
    }
  })

  return p
}

// function sum(a, b) {
//   return a + b
// }

// function extend(a, b) {
//   return { ...a, ...b }
// }

// genTest(extend)({ a: 2 }, { b: 3 })