types of testing / definitions

• unit testing I believe is testing individual classes and functions

• end to end testing
  is more complex and tries to simulate user behaviour. I think the 'end to end' term comes from trying to test both 'ends' of an app (front-end -> backend). for example I could automate a program that goes to the front end, clicks around and inputs data.
  list of tools for this type of testing here: automated testing

• test driven development (TDD)
  is a methodology or philosophy of developing software where you first define requirement / how you want your code to behave before you have the actual code.
  So you first write failing tests and then write the code and features that eventually pass all the tests.
  kind of a satisfying way to develop bc you go from all red tests and make them success one by one.

language specific

javascript testing
python testing