#!/usr/bin/env python
# coding: utf-8

# # Test
# - coders/software engineers spend as much time debugging and testing their codes as they spend on developing/writing the codes
# - "To err is human, but to preserve in error is diabolic." - anonymous
# - this more than two thousand-years old proverb fits with coding
# - "Progam testing can be used to show the presence of bugs, but never to show their absence!" - Edsger W. Dijkstra
# - code coverage is used to measure the degree to which the source code of a program is executed when a particular test suite runs
# - various coverage criteria:
#     - function coverage
#     - statement coverage
#     - branch coverage
#     - condition coverage
#     - loop coverage
#     - data-flow coverage
#     - function entry/exit coverage
# - full path coverage is usually impractical or impossible; module with a succession of n decision in it can have up to 2<sup>n</sup> paths; loops can result in an infinite number of path
# 

# ## test-driven development
# - write test cases before or simultaneously along with the code implementation
# - 3 simple ways to test your code natively at the functional level
#     1. assert statements - natively supported in many languages; as we've used before
#     2. doctest - simple, interactive technique, but makes the source code look messy, as they're defined inside the same function and module
#     3. unittest - preferred; separates the code with test 

# ## doctest
# - https://docs.python.org/3/library/doctest.html
# - to check that a module’s docstrings are up-to-date by verifying that all interactive examples still work as documented.
# - to perform regression testing by verifying that interactive examples from a test file or a test object work as expected.
# - to write tutorial documentation for a package, liberally illustrated with input-output examples. Depending on whether the examples or the expository text are emphasized, this has the flavor of “literate testing” or “executable documentation”.

# ### see factorial.py in utility package for doctest example

# ## unittest
# - https://docs.python.org/dev/library/unittest.html#module-unittest
# 
# ### see fib_unittest.py in utility package for unittest example

# ### exercise
# 1. Write unittest to test functions in utility/factorial.py module.

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