Implement Visual Regression Testing for Ink UI Components to Prevent CLI Display Issues

[hoteye]

Overview

Terraform CDK CLI has multiple UI rendering issues that could be prevented with automated visual regression testing. Since CDKTF already uses Ink framework and has , implementing visual regression testing would be a natural next step to ensure consistent CLI experience.

Evidence of Current UI Problems

Multiple open issues demonstrate recurring UI rendering problems:

Animation & Display Issues

• cdktf-cli: disable animations via flag #2951: "disable animations via flag" - CI environments show broken spinner animations:

• CLI: Fixed width output on deploy is unusable #3503: "Fixed width output on deploy is unusable" - Text wrapping makes output unreadable

• CLI UX: Nicer output for cdktf synth if there are no stacks in an app #2793: "Nicer output for cdktf synth if there are no stacks" - Output formatting improvements needed

• CDKTF CLI: CLI hangs if in interactive input is required during CDKTF commands #3041: "CLI hangs if interactive input is required" - Interactive component issues

Technical Context

CDKTF CLI already uses rich Ink ecosystem:

• (v3.2.0) - Main UI framework
• (v4.0.3) - Loading animations
• (v4.2.2) - Selection components
• (v3.1.0) - Table displays
• (v2.1.0) - Existing testing foundation

Proposed Solution: Enhanced Visual Testing

I recommend implementing ink-visual-testing alongside the existing for comprehensive UI testing.

Why ink-visual-testing for CDKTF?

• ✅ Perfect compatibility: Works with Ink v3+ (CDKTF uses v3.2.0)
• ✅ CI-focused: Specifically designed to solve CI animation issues like cdktf-cli: disable animations via flag #2951
• ✅ Easy integration: Complements existing setup
• ✅ Cross-platform consistency: Bundled fonts ensure identical rendering across environments
• ✅ Real terminal rendering: Uses node-pty for accurate CLI simulation

Implementation Benefits

1. Solve CI animation issues (cdktf-cli: disable animations via flag #2951) - Detect broken spinner rendering automatically
2. Prevent layout problems (CLI: Fixed width output on deploy is unusable #3503) - Catch width/wrapping issues before release
3. Ensure component stability - Verify ink-table, ink-select-input display correctly
4. Cross-platform consistency - Identical rendering on Mac/Linux/Windows/CI
5. Release confidence - Visual baselines prevent UI regressions

Example Implementation

import { fixedPtyRender, getCIOptimizedConfig } from 'ink-visual-testing';

// Test main CDKTF CLI commands
describe('CDKTF CLI Visual Tests', () => {
  it('should render help command correctly', async () => {
    await fixedPtyRender(
      './dist/bin/cdktf.js',
      './tests/__output__/help-command.png',
      {
        ...getCIOptimizedConfig(), // Solves CI animation issues
        args: ['--help'],
        cols: 120,
        rows: 40
      }
    );
  });

  it('should handle synth output properly', async () => {
    await fixedPtyRender(
      './dist/bin/cdktf.js', 
      './tests/__output__/synth-command.png',
      {
        ...getCIOptimizedConfig(),
        args: ['synth'],
        cols: 100,
        rows: 30
      }
    );
  });
});

Recommended Test Coverage

1. Core commands: cdktf deploy, cdktf synth, cdktf init
2. Interactive components: Selection prompts, confirmation dialogs
3. Progress displays: Spinners, progress bars, status tables
4. Error states: Error messages, warnings, validation output
5. Different terminal sizes: Narrow (80 cols) to wide (120+ cols)
6. CI environment: Animation-free rendering for automation

Integration with Existing Testing

Visual testing would complement existing tools:

• ink-testing-library: Continue for unit/component testing
• ink-visual-testing: Add for integration/regression testing
• Jest: Orchestrate both types of tests

// Existing unit test (keep these)
import { render } from 'ink-testing-library';

// New visual test (add these)
import { visualTest } from 'ink-visual-testing';

describe('Deploy Command', () => {
  // Unit test - fast, logic verification
  it('should render deploy status', () => {
    const { lastFrame } = render(<DeployStatus status="deploying" />);
    expect(lastFrame()).toContain('Deploying');
  });

  // Visual test - end-to-end, regression protection  
  it('should display deploy output correctly', async () => {
    await visualTest('deploy-output', './fixtures/deploy-command.tsx', {
      cols: 100,
      rows: 25
    });
  });
});

Technical Support Offer

I'm the author of ink-visual-testing and would be happy to provide comprehensive technical support for implementing visual regression testing in CDKTF:

1. Integration guidance - Help set up visual tests alongside existing ink-testing-library
2. CI optimization - Specifically address cdktf-cli: disable animations via flag #2951 animation issues in CI environments
3. Baseline establishment - Assist with creating initial visual baselines for key commands
4. Performance optimization - Ensure tests run efficiently in CI/CD pipelines
5. Component-specific testing - Handle complex Ink components like tables and spinners

Expected Impact

• Solve CI animation issues (cdktf-cli: disable animations via flag #2951) through consistent, animation-free CI rendering
• Prevent layout regressions (CLI: Fixed width output on deploy is unusable #3503) with automated width/formatting checks
• Improve developer confidence with visual baselines for UI changes
• Better user experience through consistent CLI appearance across platforms
• Faster debugging of UI issues with visual diff images

Next Steps

If you're interested in exploring this approach, I'm available for:

• Technical discussion on integration strategy
• Demo/proof of concept implementation
• Documentation and best practices guidance
• Long-term maintenance and support

This would significantly enhance CDKTF's reliability and solve existing UI pain points while building on your current testing infrastructure.

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Note: ink-visual-testing successfully prevents similar UI issues in other Ink-based CLIs. It's specifically designed to work alongside ink-testing-library for comprehensive testing coverage.