text: let assert = require('chai').assert;
  let {createCalculator} = require('./Add-Subtract');
  
  describe('createCalculator', () => {
      it('get the internal sum', () => {
          let result = createCalculator();
          assert.equal(0, result.get());
      });
      it('get the internal sum', () => {
          let result = createCalculator();
          result.add(1);
          assert.equal(1, result.get());
      });
      it('get the internal sum', () => {
          let result = createCalculator();
          result.add('1');
          assert.equal(1, result.get());
      });
      it('get the internal sum', () => {
          let result = createCalculator();
          result.add('-1');
          assert.equal(-1, result.get());
      });
      it('get the internal sum', () => {
          let result = createCalculator();
          result.subtract(1);
          assert.equal(-1, result.get());
      });
      it('get the internal sum', () => {
          let result = createCalculator();
          result.subtract('1');
          assert.equal(-1, result.get());
      });
      it('get the internal sum', () => {
          let result = createCalculator();
          result.subtract('-1');
          assert.equal(1, result.get());
      });
  });