Legibility fix
Code formatting fix
Test for exercise 3.10
Test for exercise 3.11
Test for exercise 3.12
Test for exercise 3.14
Test for exercise 3.15
Test for exercise 3.16
Test for exercise 3.17
Test for exercise 3.18
Test for exercise 3.18
Test for exercise 3.19
Test for exercise 3.20
Test for exercise 3.21
Test for exercise 3.22
Test for exercise 3.23
Test for exercise 3.24
Add a TreeTest
Test for exercise 3.25
Test for exercise 3.26