it('should searches a string from right to left for a pattern and returns a substring consisting of the characters in the string that are to the left of the pattern or all string if no match found', () => {
    const template = Handlebars.compile('{{str_left_back str pat}}');

    expect(template({str: 'This_is_a_test_string', pat: '_'})).toBe('This_is_a_test');
    expect(template({str: 'This_is_a_test_string', pat: 'This'})).toBe('');