Pro tip: learn to distinguish! Your friends and colleagues will be amazed! Library: your code calls it. Framework: it calls your code.
OH "Code is like humour: if you have to explain it, it's bad." /via @housecor
I've been doing Test-Driven Development for more than 10 years, and I'm still learning. Don't expect to be proficient after a 3-day course.
TDD is about feedback; if a test is painful to write, make the SUT easier to use. Unfortunately, some people tolerate pain too well.
If tests are difficult to write, it means that the System Under Test is difficult to use. (Periodic reminder)