Comments counter tests:

__mocks__/commentsCounter.js

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+export default (data) => {
+  let count = 0;
+  if (data && data.length > 0) {
+    count = data.length;
+  }
+  return count;
+};

__mocks__/commentsData.js

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+export default [
+  {
+    user_id: 1,
+    name: 'name',
+    comment: 'comment',
+  },
+  {
+    user_id: 2,
+    name: 'name',
+    comment: 'comment',
+  },
+  {
+    user_id: 3,
+    name: 'name',
+    comment: 'comment',
+  },
+  {
+    user_id: 4,
+    name: 'name',
+    comment: 'comment',
+  },
+];

__test__/commentsCounter.test.js

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+import commentsCounter from '../__mocks__/commentsCounter.js';
+import data from '../__mocks__/commentsData.js';
+
+describe('Testing commentsCounterFunction', () => {
+  it('should return the correct number of comments', () => {
+    const count = commentsCounter(data);
+    expect(count).toBe(4);
+  });
+
+  it('should have a length of greater than 0', () => {
+    const value = 0;
+
+    const count = commentsCounter(data);
+
+    expect(count).toBeGreaterThan(value);
+  });
+});