Testing: expected vs actual — App development for students
Testing checks that an app follows its rules. A test case is an input together with its expected result, worked out from the rule. Run the code with the input to get the actual result: if actual equals expected, the test passes; if not, it fails and there is a bug. Bugs love edge cases — values right at a limit, like age 12 for “under 12” — so good testers always include the limit itself.
Expected vs actual — “run each test case and compare what happens with what should happen”
Test case = input + expected result (from the rule).
Run the code: actual = expected → pass; otherwise → fail.
Always test the edge value: < and <= differ only there.
Use it for: Checking your app before release and writing good test cases for school projects.
Worked example: 🧪 One test case fails. Which one?
🚚 Rule: delivery is free (0) when the order is 500 or more; otherwise it costs 40.
function delivery(total) {
if (total > 500) {
return 0;
}
return 40;
}
Test 1: delivery(750) → expected 0
Test 2: delivery(450) → expected 40
Test 3: delivery(500) → expected 0 → Test 3
The rule says 500 or more (>=); the code tests > 500.
For 500 the code returns 40, but 0 is expected — Test 3 fails.
Check: Tests 1 and 2 pass; changing > to >= fixes Test 3 ✓
Work it out in your head or on paper, then tap your answer — or type it and press Check. Stuck? Press “Show me how”.
Right: 0 · Tried: 0
🏁 Lesson 22 test
20 questions. Check each answer, then go to the next one. Get 16 or more right to pass.
🏅 Sign in with Google to earn the
🧪 Test Case Tester badge when you pass — and a certificate when you finish all 8 lessons of
Part 3 · Logic and Building. You can still take the test without signing in.
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