fix: make it possible to count recursion calls

src/recursive-depth.js

@@ -1,3 +1,5 @@
-module.exports = function calculateDepth(arr) {
-    // write your code here
-};
+module.exports = class MyClass {
+    calculateDepth(arr) {
+        // magic
+    }
+}

test/recursive-depth.test.js

@@ -4,16 +4,17 @@ const sinon = require('sinon');
 
 Object.freeze(assert);
 
-const calculateDepth = require('../src/recursive-depth.js');
+const MyClass = require('../src/recursive-depth.js');
+const instance = new MyClass();
+const calculateDepth = instance.calculateDepth.bind(instance);
 
 const createFlatArr = (length) => Array.from({length}, () => Math.floor(Math.random() * length));
 
-
 describe('Recursive depth', () => {
     //Presence requirement
     describe('variable presence', () => {
         it('function calculateDepth exists', () => {
-            expect(calculateDepth).to.exist;
+            expect(instance.calculateDepth).to.exist;
         });
     });
 
@@ -36,9 +37,10 @@ describe('Recursive depth', () => {
             assert.equal(calculateDepth([1, [8, [[]]], [[[[[[[[[[[[[[[[[[[[[[[[[[[[[[]]]]]]], []]]], []]]]]]]]], []]]], []]]]]]]]]], 2, 3, [8, [[[[[[[[[[[[[[]]]]]]]]]]]]]]], [8, [[[[[[[[[[[[[[[[[[[[[[[]]]]]]]]]]]]]]]]]]]]]]]], 4, 5, ['6575',['adas', ['dfg', [0]]]]]), 31);
         });
         it('works recursively?', () => {
-            const spy1 = sinon.spy(calculateDepth);
-            assert.equal(spy1([1, 2, 3, 4, 5, [1, []]]), 3);
+            const spy1 = sinon.spy(instance, 'calculateDepth');
+            assert.equal(calculateDepth([1, 2, 3, 4, 5, [1, []]]), 3);
             expect(spy1.callCount).to.be.greaterThan(1);
+            spy1.restore();
         });
     });
 });