NES Test Playground — Instructions

These tests are designed so that the source files contain no hints about what Mercury is supposed to predict. All cursor placements and expected behaviors live here. Don't open this file inside the Dev Host while testing — keep it in a separate window so the model can't see it.

One-time setup

bun run watch is already running for the kilocode extension.
In the kilocode VSCode window, press F5 → opens the Extension Development Host.
In the Dev Host: File → Open Folder… → packages/kilo-vscode/docs/nes-examples/ inside this repo.
Open Settings (Cmd+,), confirm:
- kilo-code.new.autocomplete.enableAutoTrigger → ✓ (default true)
- kilo-code.new.autocomplete.model → Mercury Next Edit (Inception) ← NOT "Mercury Edit 2", which is the classic FIM option
- kilo-code.new.autocomplete.nextEdit.apiKey → your sk_... key
- VSCode global editor.inlineSuggest.enabled → ✓
To watch the pipeline live: View → Output → pick the "Kilo Code · Next Edit" channel.

Conventions used below

Cursor placement: where to click in the file before waiting.
Expected (editor): what should appear on screen.
Expected (channel): a stripped-down line you should see in the Next Edit output channel.
Path: which NES rendering path this exercises — same-line ghost / off-cursor replace / off-cursor insert / suppressed.

After each test, don't accept if you want to re-run it — the suggestion will edit the file. Either Cmd+Z after accept, or just navigate to the next test file.

Core tests (Python)

01 — Finish a function body (path: same-line insert)

File: 01_finish_function_body.py
Cursor: the empty indented line at the end of factorial (column 4).
Expected editor: ghost text proposing the recursive case.
Expected channel: diff at lines [N..N], cursor at line N, then RENDER.

02 — Pattern continuation (path: same-line ghost)

File: 02_pattern_continuation.py
Cursor: end of the last line (after COLOR_BLUE = ).
Expected editor: ghost text appending a hex color.
Expected channel: diff at lines [N..N], cursor at line N, then RENDER.

03 — Mid-identifier completion (path: same-line ghost)

File: 03_typo_completion.py
Cursor: end of the file (after return tot).
Expected editor: ghost text completing the identifier.
Path: same-line.

04 — Loop body inference (path: same-line insert)

File: 04_loop_body.py
Cursor: the empty indented line inside the for loop (column 8).
Expected editor: ghost text proposing the accumulator update.

05 — Sibling method body (path: same-line insert)

File: 05_class_method.py
Cursor: empty indented line inside pop (column 8).
Expected editor: ghost text proposing the pop body.

Advanced Python tests

07 — Multi-line rename refactor (path: off-cursor replace)

File: 07_multiline_rename_refactor.py
Cursor: end of the line with def compute_user_score(user_id, weight): (the renamed signature). The body below still uses the old u / w names.
Expected editor: strikethrough on the body lines + ghost showing the renamed body.
Tab: jump, then apply.

08 — Mixed insert + replace (path: off-cursor replace, multi-line)

File: 08_mixed_insert_and_replace.py
Cursor: end of line total = 0.
Expected editor: a decoration spanning the for-loop area showing the corrected accumulator body. The proposed text is longer than the original.

10 — Mid-token completion (path: same-line ghost)

File: 10_mid_token_completion.py
Cursor: end of the file (after result = fib).
Expected editor: ghost extending the identifier and supplying a call.

11 — Stub method with implemented siblings (path: same-line insert)

File: 11_fill_sibling_method.py
Cursor: empty indented line inside dequeue (column 8).
Expected editor: ghost text filling in the FIFO body.

12 — Type annotation insertion (path: same-line replace OR off-cursor replace)

File: 12_type_annotation_insertion.py
Cursor: on line def add(a, b): (anywhere on that line works; end-of-line is easiest).
Expected editor: strikethrough + ghost showing the typed signature. May render as inline ghost depending on where you place the cursor on the line.

13 — Docstring generation (path: same-line insert)

File: 13_docstring_generation.py
Cursor: empty indented line directly under def parse_iso_date(s): (column 4).
Expected editor: ghost text starting with """ and a one-line description.

14 — No-op suppression (NEGATIVE) (path: suppressed)

File: 14_no_op_suppression.py
Cursor: end of return a + b.
Expected editor: NOTHING. No ghost, no decoration.
Expected channel: either identical replacement — no-op or no RENDER line.
Fail mode: any visible suggestion is a false positive.

TypeScript

ts_07 — Array transform (same-line)

File: ts_07_array_transform.ts
Cursor: end of return users inside getActiveUserNames.
Expected editor: ghost text completing a .filter(...).map(...) chain.

ts_08 — Param type annotations (off-cursor replace)

File: ts_08_param_types.ts
Cursor: end of file (after main();).
Expected editor: strikethrough on add(a, b) signature + ghost showing the typed version.

ts_09 — React event handler (same-line insert)

File: ts_09_jsx_handler.tsx
Cursor: empty indented line inside handleClick (column 4).
Expected editor: ghost text incrementing count.

Go

go_07 — Error handling (same-line insert, multi-line)

File: go_07_error_handling.go
Cursor: empty line right after data, err := os.ReadFile(path).
Expected editor: ghost text proposing the canonical if err != nil { return nil, err } block.

go_08 — Struct method body (same-line insert)

File: go_08_struct_method.go
Cursor: empty indented line inside Area().
Expected editor: ghost text computing area from Width and Height.

go_09 — Goroutine + channel (same-line insert, multi-line)

File: go_09_goroutine_channel.go
Cursor: empty indented line inside the goroutine.
Expected editor: ghost text producing values onto the channel and closing it.

Rust

rs_07 — Match-arm completion (same-line)

File: rs_07_match_arms.rs
Cursor: empty indented line inside the match s { body, after the Square arm (column 8).
Expected editor: ghost text proposing the missing Rectangle and Triangle arms.

rs_08 — Result chaining (same-line ghost)

File: rs_08_result_chain.rs
Cursor: end of the line let n = s.trim() (no semicolon yet).
Expected editor: ghost text continuing the chain into a parsed i32.

rs_09 — Lifetime annotation (off-cursor replace)

File: rs_09_lifetimes.rs
Cursor: end of the file (after main's closing }).
Expected editor: strikethrough on the fn longest(...) signature + ghost showing the lifetime-annotated version.

JavaScript

js_07 — Async/await (same-line insert, multi-line)

File: js_07_async_await.js
Cursor: empty indented line inside the try { block (column 8).
Expected editor: ghost text completing fetch + json parse.

js_08 — Express route handler (same-line insert, multi-line)

File: js_08_express_route.js
Cursor: empty indented line inside the GET handler (column 4).
Expected editor: ghost text implementing get-by-id (lookup, 404, json response).

SQL

sql_07 — JOIN clause (same-line ghost)

File: sql_07_join.sql
Cursor: end of the line FROM orders o.
Expected editor: ghost text completing the JOIN against customers.

sql_08 — WHERE filter (same-line ghost)

File: sql_08_where_filter.sql
Cursor: end of the bare WHERE line.
Expected editor: ghost text proposing a predicate.

Markdown (negative)

md_07 — Prose, should stay quiet (suppressed)

File: md_07_prose_negative.md
Cursor: end of the last sentence.
Expected editor: NOTHING (ideally). If Mercury does propose a continuation of the prose, note it as a soft fail — code models writing your README isn't the v0 product.

Troubleshooting

No log lines appearing: confirm the output channel is "Kilo Code · Next Edit". Also confirm you reloaded the Dev Host after rebuilding.
[NES] skip — no API key resolved: setting wasn't saved. Re-paste the key, hit Enter, reload.
[NES] <- 400: regression on prompt shape — capture the body in the channel and ping the integration owner.
Visible suggestion that's not in this doc: write it down. Unexpected wins (or false positives) are the most useful signal.