Test cases

A set of inputs and expected outputs.

Components include…

1. Boilerplate / metadata
2. Pre-conditions
3. Inputs
4. Expected outputs
5. Observed outputs
6. Pass/fail
   1. This may not always be obvious such as in the case where we are testing Performance.
   2. Flaky tests turn a pass fail into a confidence value / probability

Creating Test Cases

The key question for creating tests for a path are:

• How do we make the path execute and how do we generate input data that satisfies all conditions on the path Key Items:
• Input vector
  • A collection of all data entities read by the routine whose values must be fixed prior to entering the routine
  • Members include:
    • Input arguments to the routine
    • Global variables and constants
    • Files
    • Network connections
    • Timers
• Predicate
  • A logical function evaluated at a decision point
  • These are basically the expressions in if, while loops etc
• Path predicate
  • This is the set of predicates associated with a path
• Predicate interpretation
  • A path predicate may contain local variables
  • Local variables play no role in selecting inputs that force a path to execute
  • Local variables are eliminated with Symbolic Execution
• Path predicate expression
  • This is an interpreted path predicate
  • This has
    • No local variables
    • A set of constraints in terms of the input vector, and maybe constraints
    • By solving the constraints, inputs that force each path can be generated
    • If a path predicate expression has no solution, the path is infeasible
• Create test input from path predicate expression

Path Predicate Example

Now we solve for a and b.

A program unit may contain a large number of paths. Selecting paths becomes a tradeoff.