Add test coverage

[davidggevorgyan]

Cover scenarios from:

• https://www.testingexcellence.com/testing-e-commerce-websites/
• https://artoftesting.com/manualTesting/ecommerce.html
• https://www.loginradius.com/engineering/test-cases-for-your-e-commerce-payment-gateway-page/

[davidggevorgyan]

I think only search tests left.
Still, there are many not covered features. Just don't want to lose time on that.