Move unittest examples to their own directory

Author: gjbex

source-code/testing/README.md

@@ -3,18 +3,15 @@
 Testing is an integral part of the software development process.  Unit
 testing is a popular technique, and is used in test-driven development
 (TDD).  Python's `unittest` module in its standard library is quite
-versatile.
+versatile, but more modern packages are available.
 
 ## What is it?
 
-1. `Simple`: a simple example demonstrating useful assertion function in
-    unittest`.
-1. `Fixtures`: an example of the use of fixtures for unit testing in the
-    context of database testing.
+1. `Unittest`: illustration of using the unittest` framework in
+   Python's standard library.
 1. `PyTest`: `pytest` is a more modern and convenient testing framework
     than that provided by Python's standard library.
 1. `Asserts`: `assert` is a Python statement, so it not part of unit
     testing per se.  It is mainly intended for contract-based programming
     and one can prevent code to be emitted for asserts by using the
     `-O` optimizatino flag when running the code.
-1. `Newick`: illustration of unit testing on real world code.