test: fix flaky SelectionFeatureIT test

[javier-godoy]

Close #107

What this PR does

This PR fixes intermittent failures in SelectionFeatureIT and other integration tests by ensuring the terminal's write queue is flushed after each sendKeys() call.

The Problem

xterm.js processes terminal.write() calls asynchronously for performance. When our key handlers call terminal.write() with escape sequences, the buffer update happens later in the event loop. Our test assertions were sometimes running before the buffer was updated, causing flaky failures.

The Fix

Modified XTermElement.sendKeys() to use executeAsyncScript with xterm's write callback:

@Override
public void sendKeys(CharSequence... keysToSend) {
    input.sendKeys(keysToSend);
    executeAsyncScript(
        "var callback = arguments[arguments.length - 1]; " +
        "this.terminal.write('', callback);"
    );
}

The empty write('') with a callback ensures all pending writes are processed before the script returns, making the test deterministic.

Why not Thread.sleep() or waitUntil()?

• Thread.sleep(): Works but is non-deterministic (and slows down tests unnecessarily)
• waitUntil(): Doesn't help because the buffer value doesn't change between polls until the write queue is flushed. The polling reads the same stale buffer value repeatedly and there's no observable state change to wait for.

Testing

• Ran SelectionFeatureIT multiple times consecutively with no failures

Summary by CodeRabbit

• Tests
  • Expanded selection feature test suite with additional test scenarios covering text selection, cursor positioning, and deletion operations.
  • Enhanced test synchronization to ensure proper Vaadin readiness before test execution.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

The changes address flaky integration tests caused by asynchronous terminal write processing in the XTerm add-on. Test infrastructure is updated to include Vaadin readiness checks, test scenarios are expanded into separate numbered methods for better isolation, and the element's sendKeys method is enhanced with an async callback to ensure terminal write completion. Copyright years are updated to 2026 across affected files.

Changes

Cohort / File(s)	Summary
Test Infrastructure Setup src/test/java/com/flowingcode/vaadin/addons/xterm/integration/AbstractViewTest.java	Updated copyright to 2026; added getCommandExecutor().waitForVaadin() call in test setup to ensure Vaadin readiness before test execution proceeds.
Test Scenario Expansion src/test/java/com/flowingcode/vaadin/addons/xterm/integration/SelectionFeatureIT.java	Renamed original testSelectionFeature() to testSelectionFeature1() and added four new test methods (testSelectionFeature2 through testSelectionFeature5) that isolate distinct selection, cursor position, and deletion scenarios with independent test initialization and assertion patterns.
Terminal Write Async Handling src/test/java/com/flowingcode/vaadin/addons/xterm/integration/XTermElement.java	Updated copyright to 2020-2026; enhanced sendKeys() method with asynchronous script callback that invokes terminal write with callback to signal completion and ensure buffer updates are processed before test assertions.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'test: fix flaky SelectionFeatureIT test' accurately summarizes the main objective: fixing flakiness in the SelectionFeatureIT test, which is the core focus of this PR.
Linked Issues check	✅ Passed	The PR successfully addresses all coding requirements from issue #107: adding waitForVaadin synchronization, flushing terminal write queue via executeAsyncScript callback in sendKeys, expanding test coverage via multiple test methods, and achieving deterministic behavior without non-deterministic sleeps.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to fixing flaky integration tests: copyright year updates are maintenance, AbstractViewTest adds Vaadin synchronization, XTermElement implements write-queue flush logic, and SelectionFeatureIT expands test scenarios—all aligned with issue #107 objectives.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud