Review Diff — Extended UX Scenario Catalogue

Scenarios planned for the second pass of the NN/g usability study. Scenarios already covered in the first report (REVIEW_DIFF_NNG_USABILITY_EVAL.md) are not repeated here.

Format: each scenario has an ID, Intent (what we're testing), Setup, User actions, and the Heuristic(s) it probes.

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A. Content / Encoding Edge Cases

S1 — Unicode & emoji in diff

• Intent: Does the renderer mangle multi-byte glyphs or wide chars?
• Setup: File containing 日本語, 🦀, combining chars, RTL Hebrew.
• Actions: Open Review Diff → observe column alignment in both panes.
• Heuristic: H3 (standards), H5 (aesthetic).

S2 — Very long line (2,000 chars on one line)

• Intent: Horizontal overflow / wrapping / scrolling behavior.
• Setup: Modify a file so a single changed line is 2,000 chars.
• Actions: Scroll horizontally; drill into side-by-side.
• Heuristic: H5, H1.

S3 — CRLF vs LF line endings

• Intent: Does the diff highlight line-ending-only changes?
• Setup: Change file from LF to CRLF (core.autocrlf off).
• Actions: Open Review Diff.
• Heuristic: H1 (visibility).

S4 — File with no trailing newline

• Intent: Does the "\ No newline at end of file" marker appear?
• Setup: Remove final newline from an existing file.
• Actions: Open Review Diff.
• Heuristic: H3 (standards).

S5 — Binary file change

• Intent: Does the editor crash or show a graceful "binary" message?
• Setup: Modify a PNG / small binary file.
• Actions: Open Review Diff, drill into side-by-side.
• Heuristic: H9 (error handling).

S6 — Only-additions file (pure new content in existing file)

• Intent: Header rendering when - count is zero.
• Setup: Append 10 lines to an existing file, no removals.
• Actions: Observe hunk header.
• Heuristic: H3.

S7 — Only-deletions file

• Intent: Symmetric to S6.
• Setup: Remove 10 lines from an existing file.
• Actions: Observe hunk header, side-by-side alignment.
• Heuristic: H3.

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B. Repository / Git State Edge Cases

S8 — Review Diff in non-git directory

• Intent: How does the feature fail when git is absent?
• Setup: cd /tmp (no .git), launch fresh, run Review Diff.
• Actions: Observe error path.
• Heuristic: H9 (error messages).

S9 — Review Diff with zero changes

• Intent: Empty-state layout.
• Setup: Clean repo, no modifications.
• Actions: Run Review Diff.
• Heuristic: H1, H5.

S10 — File rename detection

• Intent: Does git-style rename tracking show up?
• Setup: git mv foo.py bar.py without content change.
• Actions: Open Review Diff.
• Heuristic: H3.

S11 — Chmod-only change

• Intent: Does a mode-only change render cleanly?
• Setup: chmod +x file.txt with no content change.
• Actions: Review.
• Heuristic: H3.

S12 — Staged + unstaged changes on the same file

• Intent: Split-hunk behavior and grouping.
• Setup: Modify file, git add, modify again.
• Actions: Observe whether both appear and which is "current".
• Heuristic: H1.

S13 — Merge conflict file

• Intent: Does Review Diff handle <<<<<< markers sanely?
• Setup: Force a merge conflict.
• Actions: Review.
• Heuristic: H9.

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C. Terminal / Layout

S14 — Small terminal (80 × 24)

• Intent: Can the split-pane layout survive?
• Setup: Relaunch with tmux new-session -x 80 -y 24.
• Actions: Open Review Diff, toggle focus, drill in.
• Heuristic: H5.

S15 — Very wide terminal (220 cols)

• Intent: Does whitespace explode? Is column width capped?
• Setup: 220×45 tmux.
• Actions: Review.
• Heuristic: H5.

S16 — Resize mid-review

• Intent: Regression check for BUG-2.
• Setup: 160×45, open review, resize to 100×30.
• Actions: tmux resize-window or equivalent.
• Heuristic: H9.

S17 — Review Diff tab next to editing buffers

• Intent: Tab-bar behavior; does Review Diff survive buffer switches?
• Setup: Open two files, then open Review Diff.
• Actions: Cycle buffers; return to Review Diff tab.
• Heuristic: H2 (freedom).

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D. Staging / Comment Workflows

S18 — Stage then review

• Intent: A staged hunk should appear under "Staged", not "Changes".
• Setup: git add happy.py, then Review Diff.
• Actions: Observe section grouping.
• Heuristic: H1, H3.

S19 — Discard hunk confirmation

• Intent: Safety of destructive key d.
• Setup: Open Review Diff with changes.
• Actions: Press d — expect a confirm dialog.
• Heuristic: H9 (error prevention).

S20 — Add a line comment and verify persistence

• Intent: Round-trip test of c → inline render (BUG-6 regression).
• Setup: Standard changes.
• Actions: Focus diff pane, press c, type comment, Enter. Verify.
• Heuristic: H1.

S21 — Edit / delete comment

• Intent: Undo path for comments.
• Setup: After S20, press x.
• Actions: Observe removal.
• Heuristic: H2.

S22 — Export review to markdown

• Intent: Does export succeed and write a sensible file?
• Setup: After S20.
• Actions: Press e; inspect .review/session.md.
• Heuristic: H4.

S23 — Export to JSON

• Intent: Second export path.
• Setup: Use palette → Review: Export to JSON.
• Actions: Inspect .review/session.json.
• Heuristic: H4.

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E. Navigation / Discoverability

S24 — Arrow keys vs vim keys in files pane

• Intent: Are both bindings reachable? Any inconsistency?
• Setup: Any review session.
• Actions: Alternate Up/Down with j/k.
• Heuristic: H7 (flexibility).

S25 — Home/End/PageUp/PageDown in files pane

• Intent: Boundary clamping.
• Setup: 5+ files.
• Actions: Spam PageUp, End, Home.
• Heuristic: H5.

S26 — N (capital) vs n key collision

• Intent: Easy user mistake — does capital-N "Note" trigger instead of next-hunk?
• Setup: Focus diff pane.
• Actions: Press n, then N.
• Heuristic: H3, H9.

S27 — Menu-bar discoverability of Review Diff

• Intent: Can a user find the feature without Ctrl+P?
• Setup: Launch, press F10.
• Actions: Browse menus (File/Edit/View/Selection/Go/LSP/Help).
• Heuristic: H6 (recognition over recall).

S28 — Help screen

• Intent: Is there an in-app help with Review Diff keybindings?
• Setup: Press F1 / check Help menu.
• Actions: Search for "review".
• Heuristic: H10 (help & documentation).

S29 — Re-opening Review Diff after close

• Intent: Does state reset cleanly or crash?
• Setup: Open, close (q), reopen via palette.
• Actions: Verify listing matches current git state.
• Heuristic: H9.

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F. Theming / Accessibility

S30 — NO_COLOR env var

• Intent: Does the feature degrade gracefully without color?
• Setup: NO_COLOR=1 fresh.
• Actions: Open Review Diff; verify -/+ glyph still conveys change.
• Heuristic: Accessibility, H3.

S31 — Alternate theme (dark→light or high-contrast)

• Intent: Do red/green remain distinguishable?
• Setup: Switch theme via settings.
• Actions: Review.
• Heuristic: Accessibility.

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G. Performance / Scale

S32 — 50-file change set

• Intent: Files-pane scrolling and responsiveness with many rows.
• Setup: 50 modified files.
• Actions: Review, scroll files list.
• Heuristic: H4.

S33 — Single 10,000-line hunk

• Intent: Pathological large-hunk rendering.
• Setup: Replace entire contents of a 10k-line file.
• Actions: Review, scroll.
• Heuristic: Performance.

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Execution order

The scenarios above number 33. To keep the second pass tractable, execute the following high-value subset in one tmux session:

S9 (empty), S18 (staging), S20–S22 (comment round-trip + export), S14 (small terminal), S16 (resize), S27 (menu discoverability), S28 (help), S30 (NO_COLOR), S10 (rename), S6/S7 (pure-add / pure-del), S32 (many files), S1 (unicode), S2 (long lines), S4 (no newline), S29 (reopen), S19 (discard confirm), S26 (N/n collision).

Remaining scenarios are left for future expansion passes.