Rewire typescript stub private method - node.js

Question

I have the below file to test
a.ts
export function a1(param1){
a2(param1);
return result;
}
function a2(param){
return result2;
}
I am trying to write unit test case for the exported method a1 using rewire. Below is my test class
a_test.ts
const rewiredA= rewire('a');
rewiredA.__set__('a2', (token) => 'testmessage');
// Testing exported method of a.ts
rewiredA.__get__('a1')('param');
Here instead of calling the stubbed private method which returns 'testmessage', the actual private method is getting invoked. My understanding is the mocked private method will get executed, when we invoke the exported function.
Please guide me in this.

Answer 1

My understanding is the mocked private method will get executed, when we invoke the exported function.
Incorrect. If a function is not exported you cannot rewire it.
Solution
Export the function you intend to rewire. You can name it _a2 to denote that it is intended to be internal.

Answer 2

It should work for "rewire": "^4.0.1". E.g.
a.js:
function a1(param1) {
return a2(param1);
}
function a2(param) {
return 'result2';
}
a.test.js:
const rewire = require('rewire');
const mod = rewire('./a');
const { expect } = require('chai');
describe('49504977', () => {
it('a1', (done) => {
mod.__with__(
'a2',
(token) => 'testmessage',
)(() => {
const actual = mod.__get__('a1')('param');
expect(actual).to.be.eq('testmessage');
done();
});
});
it('a2', () => {
const actual = mod.__get__('a2')();
expect(actual).to.be.eq('result2');
});
});
Unit test results with 100% coverage:
49504977
✓ a1
✓ a2
2 passing (9ms)
----------|---------|----------|---------|---------|-------------------
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
----------|---------|----------|---------|---------|-------------------
All files | 100 | 100 | 100 | 100 |
a.js | 100 | 100 | 100 | 100 |
----------|---------|----------|---------|---------|-------------------
source code: https://github.com/mrdulin/expressjs-research/tree/master/src/stackoverflow/49504977