makepad-ports/docs/coverage/COVERAGE.md

Test Coverage — makepad-ports (rider · koboyo · insurance)

Measured 2026-09-01 with LLVM source-based coverage (-C instrument-coverage) on Rust 1.98.0 / cargo-llvm-cov 0.9.0 tooling, Makepad pinned at b41e7404b6bb893d32f7d2924cd7b1c28983547f + patches/.

Results

149 tests, all green: 123 engine-layer (unit + integration) + 26 UI-layer (headless full-app). Coverage below is the union of all three layers, i.e. model files are counted from unit, integration and real app binaries.

File	Lines	Regions	Functions
insurance/src/app.rs	99.57%	98.98%	100.00%
insurance/src/model.rs	100.00%	100.00%	100.00%
koboyo/src/app.rs	88.85%	89.77%	88.00%
koboyo/src/canvas_view.rs	82.48%	81.01%	94.44%
koboyo/src/model.rs	99.09%	97.35%	100.00%
rider/src/app.rs	98.19%	97.90%	100.00%
rider/src/model.rs	100.00%	100.00%	100.00%
TOTAL	95.71%	94.59%	97.88%

Raw artifacts: coverage-report.txt (llvm-cov table) and coverage.lcov (LCOV export, per-line data).

Layer mapping

Layer	What runs	What it covers
Engine	cargo test -p <crate> --lib --test integration	model.rs pure state machines (no Makepad runtime)
UI	cargo test -p <crate> --test ui (headless, MAKEPAD=headless)	app.rs + canvas_view.rs in the real release app, driven over the studio stdin protocol by the hub

Methodology

1. Everything is built with cargo llvm-cov show-env wrapper env sourced, MAKEPAD=headless exported for every cargo invocation (see landmine 3), and LLVM_PROFILE_FILE=<dir>/cov-%p-%m.profraw so every process — test harness, hub, and the spawned app — writes its own profile.

2. Test binaries build into a shared target dir; the UI harness spawns the release app via the studio hub (each crate's target/ symlinked to a shared app target dir so the hub's child build cache-hits and stays inside the 600 s startup timeout).

3. Reporting drives the LLVM tools directly (see landmine 1):

   llvm-profdata merge -sparse profraw/*.profraw -o all.profdata
   llvm-cov report --instr-profile=all.profdata \
     --object <lib-test-bin> --object <integration-bin> --object <ui-bin> ... \
     --object target/release/makepad-example-<crate> \
     --ignore-filename-regex='.*/(platform|widgets|draw|libs|studio|...)/.*|.*/main\.rs$|.*/tests/.*'
   

Exclusions (deliberate)

• Makepad framework code (platform/, widgets/, draw/, libs/, studio/): not ours; filtered by --ignore-filename-regex.
• main.rs per crate: 3-line platform startup stub (app_main!), only reachable as a process entry point outside the harness.
• Generated Makepad code: live_design! DSL blocks compile into registration code attributed to framework files, so the filter above already removes it; derived #[derive(Live, LiveHook)] impls that remain in our files are exercised by app startup in the UI layer.
• In-file #[cfg(test)] panic arms (koboyo model.rs 1170/1176/1186): panic! branches of the crate's own unit-test assertions — unreachable when tests pass.
• Mobile-only chrome (koboyo app.rs ~994-1020 dots-menu rows): the ⋮ dots_btn is visible: false at the desktop breakpoint the headless window uses, so the rows cannot be reached without viewport resizing support in the harness.

Remaining uncovered (audited, not blind spots)

• koboyo/app.rs: dots-menu rows (mobile-only, above), a few popup auto-close edges and search_input Enter-pick fallback rows.
• koboyo/canvas_view.rs: draft-preview paint for shape kinds only reachable mid-gesture with a live draft of every kind (table/browser-frame/phone frame previews), plus the selection-handles paint path for zero-size picks.
• rider/app.rs: chat list draw for the empty-history branch (933) and two timer-race guards (1091/1095, 1278-1279) — the reply/toast timers usually fire before the suite tears down; the guards need a cancel in the same tick.
• insurance/app.rs 1554: toast-expiry timer race (same class).

Test additions made for coverage (this tranche)

• koboyo: +5 integration (full key→tool map, every kind_for_tool arm + badge counter, delete/undo, content_bbox/zoom_to_fit, lasso), +4 UI (freehand gestures pen/laser/lasso/eraser/hand, select-move-delete + ⌘Z/⇧⌘Z/⌘Y, wheel zoom, ten element kinds + zoom-to-fit, rail lock/connect/export).
• rider: +1 integration (NavEffect::none), +4 UI (account rows via avatar, crosshair + Now pill, found-back + call + cancel-arriving, send button).
• insurance: +2 integration (SheetTab tables, SheetDrag translate clamps).

🐛 Real bug found and fixed by the new tests

koboyo_element_kinds_and_zoom_to_fit crashed the app (exit 101): RefCell double-borrow in the Zoom-to-fit handler — it read the canvas widget's area inside the canvas_mut closure that already held the same widget's RefCell mutably (widgets/src/widget.rs:1168: RefCell already borrowed). Fixed in koboyo/src/app.rs by reading the viewport before borrowing. The handler was previously 0%-covered — exactly the class of bug coverage work is supposed to surface.

Landmines (read before re-running)

1. cargo llvm-cov report omits example-crate objects in this workspace (0.9.0 object discovery misses them even with profdata + binaries present). Drive llvm-profdata/llvm-cov directly with explicit --object flags — the toolchain's own copies live under $RUSTUP_HOME/toolchains/<tc>/lib/rustlib/<target>/bin/.
2. SIGKILL eats app coverage. The hub terminates the child app with SIGKILL to the process group, so the LLVM runtime never flushes and app.rs reads 0%. patches/0002-hub-graceful-child-shutdown.patch closes the child's stdin first (EOF cleanly ends the headless stdin loop → atexit flush) and only escalates to SIGKILL after 5 s.
3. Keep MAKEPAD=headless set for every build. The platform build script re-runs when it changes, flipping the headless cfg and forcing a full rebuild of makepad-platform/makepad-widgets — on a small box that rebuild can OOM. Add disk-backed swap and build -j1 if RAM < 4 GB.
4. Login-shell PATH reset. The hub spawns the app via /bin/sh -lc, which resets PATH; cargo must resolve on the system default PATH (e.g. symlinks in /usr/local/bin) and RUSTUP_HOME/CARGO_HOME must be exported.
5. Per-crate target dirs. The test runtime forces CARGO_TARGET_DIR=<crate>/target for the child build; symlink each examples/<crate>/target to a shared pre-warmed release dir or the child build blows the 600 s startup timeout.
6. Never run cargo llvm-cov inside its own show-env context — it degrades to plain cargo test against the wrong target dir and rebuilds the world.