Design by contract (DbC)

• First introduced native support was in Eiffel programming language.
• Think of DbC as having if checks before and after you manipulate data inside live code. Yes they are basically assertions.
• Major components of DbC:
  • Precondition
    • Conditions that must be met before a function is executed.
    • Client obligations, supplier benefits.
  • Postcondition
    • Conditions that must be met after a function is executed.
    • Client benefits, supplier obligations.
  • Invariants
    • General rules that must be true for the entire duration of the function.
    • Conditions that must be met before and after a function is executed.

Resources

• How are TDD and DbC related?
  • TDD is external to business logic, DbC is internal.
• Code Contracts in .NET
• Design by Contract and Assertions
• Design by Contract in C3 (a successor to C)