Callable Extractor

This library is designed to help you test functions and methods that have not been exported from a file, but need to be tested. While testing the internal implementation is bad practice, there are still cases where it is necessary. One of them is to cover legacy code before refactoring.

The library is built on top of babel-parser and uses eval under the hood - so be extremely careful and use this functionality judiciously, in an isolated testing context.

Javascript, Typescript and JSX/TSX are supported.

Install

npm i callable-extractor

Usage

import { CallableExtractor } from 'callable-extractor'

test('Fetch function by name', () => {
  const ce = new CallableExtractor.fromFile(FILEPATH)
  const fn = ce.getCallableByName('myNotExportedSumFunc')
  const result = fn.call(1, 2)
  expect(result).toEqual(3)
})

test('Fetch any first callable', () => {
  const ce = new CallableExtractor.fromFile(FILEPATH)
  const fn = ce.getCallable()
  const result = fn.call(1, 2)
  expect(result).toEqual(3)
})

test('Fetch the second callable in the file', () => {
  const ce = new CallableExtractor.fromFile(FILEPATH)
  const fn = ce.getCallable(2)
  const result = fn.call(1, 2)
  expect(result).toEqual(3)
})

test('Fetch callable by line number', () => {
  const ce = new CallableExtractor.fromFile(FILEPATH)
  const fn = ce.getCallableByLineNumber(10)
  const result = fn.call(1, 2)
  expect(result).toEqual(3)
})

test('Fetch callable by line number, second in the line', () => {
  const ce = new CallableExtractor.fromFile(FILEPATH)
  const fn = ce.getCallableByLineNumber(10)
  const result = fn.call(1, 2)
  expect(result).toEqual(3)
})

test('Fetch callable by line content, partial match', () => {
  const ce = new CallableExtractor.fromFile(FILEPATH)
  const fn = ce.getCallableByLineContent('nction mySumFunc(')
  const result = fn.call(1, 2)
  expect(result).toEqual(3)
})

test('Fetch callable by name', () => {
  const ce = new CallableExtractor.fromFile(FILEPATH)
  const fn = ce.getCallableByName('mySumFunc')
  const result = fn.call(1, 2)
  expect(result).toEqual(3)
})

test('Fetch class method', () => {
  const ce = new CallableExtractor.fromFile(FILEPATH)
  const fn = ce.getCallableByName('mySumMethod', 'MyClass')
  const result = fn.call(1, 2)
  expect(result).toEqual(3)
})

test('Fetch class constructor, test with context and scope', () => {
  const ce = new CallableExtractor.fromFile(FILEPATH)
  const fn = ce.getCallableByName('constructor', 'MyClass') // constructor (a, b) { this.c = a + b + myGlobalVar }
  fn.context = { c: 0 }
  fn.scope = { myGlobalVar: 4 }
  fn.call(1, 2)
  expect(fn.context.c).toEqual(7)
})