https://www.nngroup.com/articles/why-you-only-need-to-test-with-5-users/
https://www.userlynx.com/
WYSIWYG landing page creator
https://unbounce.com/
AB testing
https://www.smashingmagazine.com/2014/07/roadmap-to-becoming-an-a-b-testing-expert/
https://www.smashingmagazine.com/2014/11/how-to-create-your-own-front-end-website-testing-plan/
https://medium.com/@Pinterest_Engineering/building-pinterests-a-b-testing-platform-ab4934ace9f4
https://medium.com/@Pinterest_Engineering/lessons-in-growth-engineering-how-we-doubled-sign-ups-from-pin-landing-pages-1c0bc400cdb9
Testing text
https://medium.com/@Pinterest_Engineering/how-we-increased-active-pinners-with-one-simple-trick-a157f0a527b9