Testing and Debugging

1
Testing and Debugging
a good tester is one who likes to break things!
a good tester is one who likes to fix things!

• Testing is the process of trying to force
  software to exhibit its defects (violations of
  contracts)
• Debugging is the process of identifying and
  fixing such defects

2
Testing a Class Step 1
this is normally an entire class, not just a
single method
a good way to present a test case is with a
tracing table

• Create a test plan, i.e., a set of test cases,
  each of which has
• A set of input values to a method of the unit
  under test (UUT)
• A set of expected output values, based on the
  methods contract

3
Testing a Class Step 2
this can be tricky

• Carry out the test plan, i.e., write a test
  driver program that for each test case
• Constructs the test case input values of the test
  case
• Executes the method
• Compares the actual output values of the method
  to the expected output values of the test case

this can be tricky
this is often just main in the UUT!
4
Test Case Selection
sometimes called black-box testing
sometimes called white-box testing or clear-box
testing

• Test cases can be
• Specification-based, i.e., selected based on the
  interface contract the UUT is supposed to
  implement
• Code-based, i.e., selected based on the code of
  the UUT
• What are some pros and cons of both?

5
Test Coverage Black Box

• Partition the input space and output space for
  each method based on the contract (look at the
  requires/ensures clauses, respectively)
• Include at least one test case from each partition

one good way to partition is to identify extreme
cases in the specification
6
Test Coverage White Box
if (condition) branch1 else branch2
if (conditionA) branch1 else
branch2 if (conditionB) branch3 else
branch4
each of these is stronger than the one before it

• Statement coverage
• Make sure each statement is executed at least
  once
• Branch coverage
• Make sure each branch is executed at least once
• Path coverage
• Make sure each path is executed at least once