Debugging & Testing
Learn the edit/validate/reload/test loop, how to read common errors, and how to prove a feature survives real gameplay.
The beginner debug loop
1. Change one thing 2. Validate 3. /reload (or restart when required) 4. Test one expected result 5. If it fails, read the first useful error 6. Fix the smallest cause 7. Repeat
Do not make ten unrelated edits and then try to guess which one broke the pack.
Start with these tools
| Tool | Use it for |
|---|---|
/reload | Reload datapack data/functions and DAI reloadable data. |
/datapack list | Check whether Minecraft sees/enables your datapack. |
logs/latest.log | Detailed Minecraft/NeoForge/DAI errors for the current run. |
| DAI Creator validation | JSON syntax, paths, duplicate IDs, known references and schema checks it can know in-browser. |
| Creator Gameplay Tester | Disposable test scenes before exporting to a real world. |
Read errors from the top of the cause chain
One broken JSON file can cause several follow-up failures. Find the earliest message that names your namespace/path.
| Symptom | First inspection |
|---|---|
| JSON parse / syntax | Open the named file; inspect commas, braces, brackets and quotes. |
| Unknown function | Check the function file path and convert it back to the expected namespaced ID. |
| Unknown action/condition/type | Check spelling, namespace, current DAI version and required parameters. |
| Missing model/texture | Check resource-pack path, namespace and file extension/case. |
| Pack not listed | Check pack.mcmeta location/schema and ZIP root. |
| Works once, breaks after reload | Initialization may not be reload-safe or state is being duplicated/reset. |
| Works single-player, not multiplayer | Temporary state may be global when it should be per-player/server-authoritative. |
Path debugging trick
When Minecraft says my_game:player/heal is missing, translate it back:
my_game:player/heal ↓ data/my_game/function/player/heal.mcfunction
Then verify every folder and the exact extension.
Syntax-valid does not mean behavior-valid
A JSON validator can prove the punctuation is legal. It cannot prove that your referenced item exists, your conditions are logically reachable, or your reward cannot duplicate. That requires Minecraft testing.
Testing ladder
- Happy path.Do the intended action once.
- Reload.Confirm the feature still works after
/reloadand save/reload where relevant. - Spam/invalid input.Try repeated clicks, empty inventory, insufficient cost, bad target and wrong state.
- Failure/recovery.Death, disconnect, void/water, transition interruption where relevant.
- Two players.Use different progression states and prove temporary/private state does not leak.
- Upgrade test.Install the new release over a copy of an old save before publishing.
When a restart is better than /reload
Use a full restart for startup-only registry/runtime changes, early-loading/branding behavior, mod-JAR changes, or when the relevant guide says a reload is insufficient. Do not assume every engine-level change is hot reloadable.
Checkpoint
You are ready when a broken pack no longer means “start over”; it means “find the named path, classify the error, make one correction, retest.”