PHP Fatal error: Class 'WP_UnitTestCase' not found - phpunit - php

Question

I know that it already has answer in PHP Fatal error: Class 'WP_UnitTestCase' not found when trying to run test-sample But it doesn't fixed my issue. I am trying to initialize php unit testing with my wordpress plugin using phpunit. I found this tutorial and it was easy to follow. Here's the link
https://www.smashingmagazine.com/2017/12/automated-testing-wordpress-plugins-phpunit/
Everything was working great until the below step.
When I came to this Step in tutorial where the command I tried to run
phpunit tests/test-sample.php
and I get:
PHP Fatal error: Class 'WP_UnitTestCase' not found in PHP Fatal error: Class 'WP_UnitTestCase' not found in /var/www/html/testwordpress/wp-content/plugins/wp-ultimate-csv-importer/tests/test-sample.php on line 11
I don't Know how to solve this issue. I found the same question in Stackoverflow. Here's the Link:
PHP Fatal error: Class 'WP_UnitTestCase' not found when trying to run test-sample
But it was in windows. Somehow he managed to fix it. I checked his solution and it says that issue in MySQL.
But in my case, MySQL works fine and I am in linux with the flavor of Ubuntu. Help me with some solutions to fix this problem in Linux