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8. Essential Tests

Level: beginner · Reading time: 3 min · Prerequisite: book/poche/07-reading-errors.html · Last review: 2026-05-09

TL;DR (5 lines)

  • Read the core idea first.
  • Understand one concept at a time.
  • Run small examples.
  • Fix errors early.
  • Move to next chapter only when clear.

Frequent mistakes

  • Skipping prerequisites.
  • Reading without trying examples.
  • Fixing too many errors at once.

Prerequisites: book/poche/07-reading-errors.html. See also: book/chapters/18-tests.html.

Goal

Write short tests that secure the basics.

Example

Nominal case + limiting case for each critical procedure.

Why it matters

Testing avoids regressions during refactors.

Quick check

What is the smallest useful test for add(a, b)?

Try this

  1. Add a nominal test.
  2. Add a limit test.
  3. Check the expected result.

If you're stuck

2 well-targeted tests are better than 20 redundant tests.

See also

Next best action

Apply one idea from this chapter in a tiny example, then continue.