Add comprehensive test suite for runtime (layout + render)

[wangnaihe]

Module

w3cos-runtime

Description

The runtime crate (layout, render, window, state) has minimal tests. Add comprehensive unit tests.

Areas to Test

• layout.rs: Verify Taffy layout computation for various Component trees (flex, grid, nested)
• state.rs: Already has 6 tests, but add edge cases (multiple signals, concurrent access patterns)
• render.rs: Snapshot tests — render a Component to a Pixmap and verify pixel values at key positions
• Integration: Build a Component tree with signals + onClick, verify state changes propagate

Acceptance Criteria

• At least 20 new tests across layout/render/state
• Test edge cases (empty trees, deeply nested, zero-size components)
• All tests pass with cargo test -p w3cos-runtime
• No new clippy warnings

Difficulty

Medium

[github-actions]

AI Triage — Auto-classified this issue.

Labels: module:runtime, module:cli, difficulty:hard, ai-ready

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[zhaog100]

I'd like to work on this! I'll add comprehensive tests for layout.rs, render.rs, and window.rs (flatten_tree). Will create a PR targeting at least 25 new tests with edge cases.

[zhaog100]

I'd like to work on this! I'll add comprehensive tests for layout.rs and render.rs.

Plan:

1. Layout tests: flex layout computation for various component trees
2. Render tests: pixel verification for rendered components
3. Edge cases: empty trees, deeply nested, zero-size components

I'll start with a PR targeting at least 20 new tests.

[wangnaihe]

Thanks @zhaog100! Your PR #23 has been approved and merged — great work on the 20 layout tests.

If you want to continue, there's more room for tests:

• Render snapshot tests (verify pixel values)
• State/signal integration tests
• Window event simulation tests

Feel free to open a follow-up PR!