19 Unit Test¶

Topics¶

• unit testing
• test-driven development
• doctest

19.1 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
• "Program 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 $2^n$ paths
  • loops can result in an infinite number of paths
• see this repository for more examples of unit testing: https://github.com/rambasnet/KattisDemos

19.2 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

19.3 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¶

19.4 unittest¶

• https://docs.python.org/dev/library/unittest.html#module-unittest

see fib_unittest.py in utility package for unittest example¶

19.5 Exercise¶

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