Add specs to auto-scroll.hook

[nasdan]

Here you have a working tests checking the scrollTop value when it calls doAutoScroll.

import { textarea } from 'pods/trainer/components/new-text.styles';
import React from 'react';
import { renderHook } from '@testing-library/react-hooks';
import { useAutoScroll } from './auto-scroll.hook';

describe('src/common/hooks/auto-scroll.hook specs', () => {
 it('should return initial values when it renders the hook', () => {
 // Arrange
 const textArea = {
 scrollHeight: 10,
 scrollTop: undefined,
 };

 jest.spyOn(React, 'useRef').mockReturnValue({
 current: textArea,
 });

 // Act
 const { result } = renderHook(() => useAutoScroll());

 // Assert
 expect(result.current.isAutoScrollEnabled).toBeTruthy();
 expect(result.current.textAreaRef.current).not.toBeNull();
 expect(result.current.textAreaRef.current.scrollHeight).toEqual(10);
 expect(result.current.textAreaRef.current.scrollTop).toBeUndefined();
 });

 it('should update scrollTop with height value when it call doAutoScroll', () => {
 // Arrange
 const textArea = {
 scrollHeight: 10,
 scrollTop: undefined,
 };

 jest.spyOn(React, 'useRef').mockReturnValue({
 current: textArea,
 });

 // Act
 const { result } = renderHook(() => useAutoScroll());

 result.current.doAutoScroll();

 // Assert
 expect(result.current.textAreaRef.current.scrollTop).toEqual(10);
 });
});

• Pending specs:
  • Disable auto scroll and check isAutoScrollEnabled value
  • Disable auto scroll, calls doAutoScroll and check it doesn't update the scrollTop value.