test: Add unit tests for basic layer operations in dispatcher

[yuvraj-kolkar17]

What this pr does

Adds basic unit tests to editor/src/dispatcher.rs for simple layer
operations that had no test coverage before

Part of #3936

After 4 new test added

• new_document_starts_empty verifies a new document starts with zero layers
• draw_rect_adds_one_layer verifies drawing a rectangle creates exactly one layer
• delete_selected_layer_reduces_count verifies deleting the selected layer reduces the count from 3 to 2
• paste_twice_gives_five_layers verifies pasting the same clipboard content twice on 3 layers gives 5 total

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request adds basic unit tests to editor/src/dispatcher.rs to cover simple layer operations that previously lacked test coverage. The new tests ensure that new documents start empty, drawing a rectangle adds a layer, deleting a selected layer reduces the layer count, and pasting content from the clipboard increases the layer count as expected.

Highlights

• New Tests: This PR introduces four new unit tests to enhance the coverage of layer operations in editor/src/dispatcher.rs.
• Layer Operations Verification: The tests verify basic functionalities such as creating a new document with zero layers, adding a layer by drawing a rectangle, deleting a selected layer, and pasting layers from the clipboard.
• Improved Test Coverage: These additions address previously uncovered areas of the dispatcher, increasing the robustness and reliability of the editor.

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[cubic-dev-ai]

1 issue found across 1 file

Confidence score: 4/5

• This PR appears technically safe to merge, with the only reported concern being PR title format enforcement rather than a code behavior defect.
• The flagged issue is high-confidence but process-oriented: the title should be updated to the required sentence-case imperative format (for example, starting with “Add”) and avoid a conventional commit prefix.
• Because the finding does not indicate a runtime regression in editor/src/dispatcher.rs, merge risk is low once repository conventions are satisfied.
• Pay close attention to editor/src/dispatcher.rs - ensure the PR metadata/title policy is corrected so checks and review workflow are not blocked.

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="editor/src/dispatcher.rs">

<violation number="1" location="editor/src/dispatcher.rs:531">
P1: Custom agent: **PR title enforcement**

Update the PR title to follow the required format (no conventional commit prefix, sentence case, imperative verb like "Add").</violation>
</file>

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[gemini-code-assist]

Code Review

The pull request adds tests for creating a new document, drawing a rectangle, deleting a selected layer, and pasting layers. The reviewer suggested using DocumentMessage::DeleteSelectedLayers instead of NodeGraphMessage::DeleteSelectedNodes in the delete_selected_layer_reduces_count test for robustness and suggested avoiding the test-only PortfolioMessage::PasteIntoFolder API in the paste_twice_gives_five_layers test.

[yuvraj-kolkar17]

PTAL @TrueDoctor @Keavon