Lesson 19 / 25

Testing

Understand Testing as a useful part of Swift.

The essential idea

Testing gives you one practical part of Swift. Start by naming the input, the change, and the expected result. This mental model matters before any syntax rule.

Run a tiny experiment

Use a minimal example. Predict what changes, run it, then explain the observed result.

// Explore Testing with one focused example.
value = 0
print(value)

Output:

0

Avoid this trap

Do not memorize Testing in isolation. Change one value in a small example and use feedback to correct your understanding.

Quick check

Quick check: What is a good first practice for Testing?

  • Run one small focused example.
  • Memorize without testing.
  • Ignore feedback.
Answer

Run one small focused example. — Small experiments reveal cause and effect.