Animation Test Migration

Convert one series type's animation coverage from manual -test docs pages and per-ratio image snapshots to frame-trajectory tests. This procedure was established on bar (PR #7358) and line (PR #7368) — read the animation -test page actions describes in barSeries.test.ts and lineSeries.test.ts as the reference implementations, and the animation-trajectory-tests rule for harness vocabulary. Work one series per PR against latest, under the AG-17755 umbrella.

Step 1 — Inventory the behaviours to cover

1. List the animation examples on the series' -test page(s) (packages/ag-charts-website/src/content/docs/<series>-series-test/_examples/*/main.ts) — each control on those examples becomes at least one trajectory CASE, in both standalone and integrated mode where the page has an integrated variant (options.mode: 'integrated'). Non-animation examples on the same page (missing-data rendering, layout variants) stay put. Some series never had a -test page — skip this sub-step and Step 7 entirely for those, and drive the CASEs from the public animation docs-page actions plus the existing spyOnAnimationManager snapshot describes instead of hunting for pages that do not exist.
2. Add the relevant public animation docs-page actions (initial load, add/remove/update data, legend toggle) if the page lacks a button for them — same code path, cheap coverage.
3. List the existing snapshot animation describes in the series' *.test.ts and classify each: trajectory-expressible (motion, timing, bounds — the default) vs pixel-only (compositing, fills, painted clipping — kept as snapshots, ratio list trimmed to [0, 0.5, 1] or endpoints).

Step 2 — Probe, then write CASEs

For each behaviour, add a temporary probe test that runs the action under spyOnAnimationFrames() and dumps sampled frames (process.stdout.write). Read the real per-frame values and phases; only then write the CASE. Reuse the suite's spec fragments (fadeIn, markersReflow, revealFromBaseline, axisReflowSpec, survivorBands) or add equivalents; shared helpers used by 2+ files belong in chart/test/utils.ts.

The moving reveal property varies by series family — box-plot uses scalingY, radar the bbox width/height, range a clip:x swipe plus marker width/height. Derive it from the probe; do NOT copy it from a sibling series' precedent. Probe the whole sampled scene, not just the mark nodes: labels, containers and stacked inner edges animate too.

Every CASE needs:

• an anti-vacuity guard (frame-0 collapsed/full-value assertion, or endpoint count change);
• phase windows (during) on everything that moves, so desync regressions fail;
• frameInvariants for cross-node contracts (stack contiguity, marker-on-path sync).

If the action snaps structurally at frame 0 (series toggles, category swaps), hand-roll the capture instead of captureUpdate (see the structural-snap pitfall in the animation-trajectory-tests rule).

Step 3 — Negative-test every spec

Flip one direction/phase/settle value per new expectation, confirm the CASE fails with a diagnostic naming the behaviour, revert. Never skip this: the vocabulary has vacuity traps.

Step 4 — Regression sanity-check against historic bugs

git log --oneline --grep=<SERIES> and trawl the CRT JIRA project for the series' historic animation bugs. For each, re-inject the defect by perturbing the CURRENT fix line (old fixes rarely revert cleanly), run the new CASEs, and record caught/missed. A missed bug means a missing CASE or invariant. Restore the source exactly (git status must be clean) before committing.

Step 5 — Convert the snapshot blocks

Delete each trajectory-covered snapshot describe, leaving a one-line pointer comment naming the covering CASE(s). spyOnAnimationManager() and spyOnAnimationFrames() cannot coexist under a shared parent scope — a spyOnAnimationManager() at a top-level describe cascades into a sibling spyOnAnimationFrames() describe. Keep any retained snapshot block's spy inside its own describe rather than hoisted above both. Trim kept pixel-only blocks' ratio lists. git rm the matching PNGs under the suite's __image_snapshots__/ (they are never auto-pruned), then run the suite and confirm no *-diff.png artifacts and no "new snapshot written" output. Snapshot deletion needs explicit user authorisation — get it before this step.

Step 6 — Pixel endpoint guards

Add 2-3 expectAnimatedEndpointsMatchStatic call sites per suite for the highest-value transitions (data update, series add/remove, legend toggle). These replace the endpoint role of the deleted 0%/100% snapshots.

Step 7 — Retire the animation examples

Only after steps 1-6 are merged-quality and the user signs off. Scope removal to the animation examples, not the whole page — a -test page often hosts unrelated examples too (e.g. area-series-test keeps missing-data-area), and only line and bar happened to be animation-only:

• delete the animation _examples/<name>/ directories the CASEs now cover, and remove their entries from the page's index.mdoc;
• remove the matching per-example keys from any '<series>-series-test' block in packages/ag-charts-website/e2e/example-options.ts;
• only if no examples remain, delete the whole packages/ag-charts-website/src/content/docs/<series>-series-test/ directory and its example-options.ts block (this is what happened for line and bar);
• grep the repo for remaining references (nav.json needs nothing — -test pages are excluded automatically).

Step 8 — Verify

• Targeted: NX_DAEMON=false npx vitest run --config packages/ag-charts-community/vitest.config.ts <suite> (enterprise config for enterprise series).
• Full: yarn nx test ag-charts-community and ag-charts-enterprise.
• Gates: yarn nx format, yarn nx lint <package>, NX_DAEMON=false yarn nx build:types <package>.