单元测试内部函数？

Question

I have a function that has inner functions, for my unit test, I only want to test the functionality of the inner function, but when I export the function and call the inner function, npm tests returns an error.

In my main.js :

mainFunction = () => {
  functionToBeTested = () => {
    // some code
  }
}

module.exports = {mainFunction: mainFunction}

In my test.js

const chai    = require("chai");
const assert  = require("chai").assert;
const mainFunction = require("./main");

describe ("test", () => {
 it("returns results", () => {
  let result = mainfunction.functionToBeTested(args);
  //equal code
  });
})

But when I run npm test, it says:

mainfunction.functionToBeTested is not a function.

What am I doing wrong?

Answer 1

If you want to chain your functions you can try something like that.

main.js

const mainFunction = () => {
  const functionToBeTested = () => {
    return "I got it";
  }
  return { functionToBeTested };
}

module.exports = { mainFunction };

test.js

const chai    = require("chai");
const assert  = require("chai").assert;
const mainFunction = require("./main");

const mf = mainFunction();

describe ("test", () => {
 it("returns results", () => {
  let result = mf.functionToBeTested(args);
    //equal code
  });
});

Answer 2

Actually, you can't call a function declare inside another function that way. A solution would be to declare functionToBeTested outside mainFunction , then call it :

main.js

const functionToBeTested = () => {
  // some code
};

const mainFunction = () => {
  functionToBeTested();
};

module.exports = { mainFunction, functionToBeTested }

test.js

const chai    = require("chai");
const assert  = require("chai").assert;
const { mainFunction, functionToBeTested } = require("./main");

describe ("test", () => {
  it("tests mainFunction", () => {
    let main = mainfunction(args);
    ...
  });

  it("tests functionToBeTested"), () => {
    let tested = functionToBeTested(args);
    ...
  });
})

Answer 3

It is because only mainFunction() is exported and not the functionToBeTested(), outside this module JS doesn't knows about the existence of the functionToBeTested().

I will recommend you to move functionToBeTested separated and export that as well or have a helper method for calling it.