PLECK lesson 136 · suggested week 28, day 1
Write tests before a small rule change
Objective. Predict behavior and encode it as assertions.
Godot Engine Standard desktop editor 4.7.2-stable, GDScript (Godot 4), Compatibility renderer. Headless Godot 4.7.2.stable.official.ed1daf0bf passed 106 assertions on the supplied scaffolds, including malformed JSON saves. Audio used the Dummy driver and a synthetic WAV, not a speaker. The visual editor, browser export, and signed-in submission were not tested. The desk still does not run a student's own upload.
About 55 minutes. The due date is chosen by a parent.
Pure functions, boundary cases, error reading and focused repair
Suggested pace: Recall and predict 5 min; Read instruction and scaffold 12 min; Build or design the assigned artifact 25 min; Run acceptance tests 8 min; Explain and checkpoint 5 min.
Materials: Godot Standard 4.7.2 desktop editor (GDScript, Compatibility renderer), Local course folder and prior checkpoint, No paid assets or public account required.
Comes after VGC-L135.
Use C-TESTS to see a small pure-function harness. The bounded_score rule adds a change and clamps the result to zero through 999. Write a new rule for a combo bonus: one through three deliveries earn two points each, while four or more earn an additional five-point bonus. Define zero and negative inputs explicitly before coding. Assertions compare actual and expected results. Start with a failing test in a duplicate or new lab, implement the function, then run all tests.
Worked example
A capacity function tested at below-minimum, middle and above-maximum inputs is easier to trust than one demonstrated only at a normal value. Scaffold C-TESTS — A tiny pure-function test harness Setup: Attach to Node TestLab. If using command line, create a separate SceneTree harness rather than running this Node script with --script. Run current TestLab scene in editor; assert reports a failed condition in Debugger. No external test framework or package is needed. ```gdscript extends Node func bounded_score(old_score: int, change: int) -> int: return clampi(old_score + change, 0, 999) func _ready() -> void: assert(bounded_score(10, 2) == 12) assert(bounded_score(0, -3) == 0) assert(bounded_score(998, 9) == 999) print("3 score checks passed") ```
A tiny pure-function test harness
GDScript (Godot 4, not Scratch, Python, JavaScript or C#). Scaffold C-TESTS. Copy starts from this text. The desk does not run it.
Scene and node setup
Attach to Node TestLab. If using command line, create a separate SceneTree harness rather than running this Node script with --script. Run current TestLab scene in editor; assert reports a failed condition in Debugger. No external test framework or package is needed.
extends Node
func bounded_score(old_score: int, change: int) -> int:
return clampi(old_score + change, 0, 999)
func _ready() -> void:
assert(bounded_score(10, 2) == 12)
assert(bounded_score(0, -3) == 0)
assert(bounded_score(998, 9) == 999)
print("3 score checks passed")
Checks to run in the editor
- All three assertions pass.
- Intentionally change expected 12 to 13 and observe a failure, then restore.
Native Godot 4.7.2.stable.official.ed1daf0bf headless compile and representative node-tree/runtime tests passed; see native-qa-results.json. Visual UI, audible output, exports and website submission still need separate checks.
Write tests before a small rule change — evidence task
- 1. Write expected results for counts -1,0,1,3,4 and 6.
- 2. Implement the rule so invalid negative counts return zero.
Deliverable. Combo-rule lab and six assertions.
Acceptance checks
- VGC-L136-T1. Expected results are 0,0,2,6,13 and 17.
- VGC-L136-T2. All six assertions pass without changing expected values to hide errors.
Understanding question. Why is the first bonus-boundary test count 4 important?
Include a downloadable project ZIP with project.godot, .tscn, .gd and original asset files when code changes. A private, teacher-accessible download link to that ZIP is equivalent. Screenshots or a playthrough do not replace editable source.
If this is still shaky. Use C-TESTS and one ordinary plus two boundary cases. Keep a known-good snapshot before injecting faults. Start with the first assigned task and re-run its acceptance test before adding the remaining feature.
Optional extra. Add a property that should hold for many inputs and test a small finite range. Document one changed parameter, your prediction, and the observed effect; optional, not required for completion.
Turn in typed notes and a JPEG, PNG, or WebP screenshot. One https address is stored as text and is not opened, extracted, or run. An MP3, WAV, M4A, MP4, or WebM file up to 4 MB can show a demo. The demo does not replace editable source. Zip and code files are refused. If there is no private link, keep the project on the family computer and review the code in person.
- Your first 2D game
Free public tutorial; no account; external asset download is optional, not used by this course.
· Opening this link does not submit the lesson.
This is a preview. A parent assigns the lesson and chooses the due date after the student is enrolled. The answer key is not on this page.