[cpsievert]

Stacked on #412.

Summary

Browser-level tests for accessor attach timing, following up #412:

• test_state_accessor_captures_gesture_before_first_read — a zoom-in gesture before a button-gated first read of ipyleaflet zoom(); the read reflects the gesture. This is a scenario-contract guard, not a feat: state-kind accessors attach eagerly at render by default #412-specific regression test: it passes both pre- and post-feat: state-kind accessors attach eagerly at render by default #412 (verified by flipping AccessorSpec.eager's default back to False), because ipyleaflet pushes synced traits unconditionally and the lazy attach's seed self-heals. What it guards is the user-visible contract against any future frontend that gates state sync on a listener existing. Attach timing itself is covered by feat: state-kind accessors attach eagerly at render by default #412's unit tests.
• test_event_accessor_misses_click_before_first_read — characterization of intentional behavior: kind="event" clicked() still attaches lazily, so a pre-read map click is missed while post-read clicks are captured. Acts as a tripwire if the event default ever changes.

The app fixture gates all accessor reads behind @reactive.event buttons and exposes a raw-trait sentinel output so tests wait for browser→server sync deterministically.

A survey of every state-kind accessor in the package (ipyleaflet, jscatter, altair, bokeh, quak, mosaic, perspective, itables, ipydatagrid, embedding_atlas, pythreejs, k3d, ipyaladin, lonboard, matplotlib) found all are trait/signal-backed with self-healing seeds; the only browser-listener-gated mechanisms are the plotly bridge (event-kind only) and the reactable bridge (state-kind, but re-seeds on bind). So no current state accessor can discriminate pre/post-#412 in a browser test — a truly discriminating test would need a listener-gated state frontend that doesn't exist in the package yet.

Verification

• New tests: 2 passed, ×4 runs, no flakes.
• Related existing suites green: ipyleaflet_accessors, ipyleaflet_marker_click, jscatter_accessors, accessor_helper.
• make check clean (the one test_geolibre failure is pre-existing on this base and already fixed on main by feat(geolibre): use geolibre's async command methods when available #360).

[Copilot]

🟡 Changes recommended

The test can pass before the first read completes and accept coordinates from the pre-read click, so it may miss an eager-listener regression without a distinct no-event value to wait for.

1 open issue

• Wait for completed empty read before testing lazy listener · New

What changed in this PR

Adds browser coverage for accessor behavior when the first read is delayed, complementing #412’s unit tests for attach timing.

Changes:

• Adds a state-accessor contract test verifying that a zoom gesture is reflected in the first read.
• Adds an event-accessor characterization test for lazy click-listener attachment.
• Introduces a fixture with button-gated reads and a raw zoom-trait synchronization sentinel.

File	Description
tests/​playwright/​ipyleaflet_eager_attach/​test_ipyleaflet_eager_attach.py	Adds browser tests for state and event behavior before the first accessor read.
tests/​playwright/​ipyleaflet_eager_attach/​app.py	Provides gated accessor reads and a zoom synchronization output.

_{Review effort: Balanced}

[Copilot]

🟢 Approval recommended

No active review issues were identified in the added browser-level coverage for accessor behavior before the first read.

No open issues 🎉

1 resolved since last review

• Wait for completed empty read before testing lazy listener

_{Review effort: Balanced}