Map of example scripts to Chapter sections

1. Python standard test tools (unittest)
  1.1 ./unittest_testing/test_primes.py

2. unittest alternatives (pytest)
  2.1 ./pytest_testing/test_primes.py

3. Building a fake
  3.1 ./test_with_fake/test_mailer.py

4. Using mocks
  4.1 ./test_with_mock/test_mailer.py
  4.2 ./test_with_mock_patch/test_mailer.py
