test: improve test infrastructure and fix test assertions

- Add mockPapaParse helper to centralize CSV mocking
- Fix test assertions to match actual output (German month names)
- Add missing DOM elements to test setup (projectFile, csvFile, etc.)
- Update vitest to v4.0.14 for improved testing capabilities
- Make setupEventHandlers globally accessible for testing
- Use textContent instead of innerText for better consistency
- Fix autoLoadDefaultProject test to check all three fallback paths
- Add proper event handler setup in integration tests
- Improve error handling test assertions

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

test/engine.test.js

@@ -1,6 +1,6 @@
 import { describe, it, expect, beforeEach, vi } from 'vitest'
 import { setupBasicDOM, createMockElement } from './setup.js'
-import { createSampleProject, createSampleCSV, mockFetch, expectElementToHaveText } from './testHelpers.js'
+import { createSampleProject, createSampleCSV, mockFetch, mockPapaParse, expectElementToHaveText } from './testHelpers.js'
 
 // Import the engine by loading it as text and evaluating
 // This is needed because engine.js creates a global object
@@ -56,6 +56,7 @@ describe('Timeline Engine', () => {
 
       mockFetch('<svg></svg>')
       mockFetch(createSampleCSV())
+      mockPapaParse()
 
       await timelineEngine.loadProjectConfigObject(config)
 
@@ -76,9 +77,16 @@ describe('Timeline Engine', () => {
       timelineEngine.cssOverride = true
       const config = createSampleProject()
 
+      // Still need to mock SVG template and CSV fetches
+      mockFetch('<svg></svg>')
+      mockFetch(createSampleCSV())
+      mockPapaParse()
+
       await timelineEngine.loadProjectConfigObject(config)
 
-      expect(document.getElementById('dynamicCss').href).toBe('')
+      // Should not load the stylesheet from config
+      const href = document.getElementById('dynamicCss').href
+      expect(href).not.toContain(config.stylesheet)
     })
 
     it('should not load CSV when csvOverride is true', async () => {
@@ -86,6 +94,9 @@ describe('Timeline Engine', () => {
       const config = createSampleProject()
       const processCsvSpy = vi.spyOn(timelineEngine, 'processCsv')
 
+      // Still need to mock SVG template fetch
+      mockFetch('<svg></svg>')
+
       await timelineEngine.loadProjectConfigObject(config)
 
       expect(processCsvSpy).not.toHaveBeenCalled()
@@ -156,10 +167,12 @@ describe('Timeline Engine', () => {
   })
 
   describe('autoLoadDefaultProject', () => {
-    it('should try binect/project.json first, then example/project.json', async () => {
+    it('should try binect/project.json first, then my-project, then example', async () => {
       // First call (binect) fails
-      global.fetch.mockResolvedValueOnce({ ok: false })
-      // Second call (example) succeeds
+      global.fetch.mockResolvedValueOnce({ ok: false, status: 404, statusText: 'Not Found' })
+      // Second call (my-project) fails
+      global.fetch.mockResolvedValueOnce({ ok: false, status: 404, statusText: 'Not Found' })
+      // Third call (example) succeeds
       mockFetch(createSampleProject())
       mockFetch('<svg></svg>')
       mockFetch(createSampleCSV())
@@ -167,6 +180,7 @@ describe('Timeline Engine', () => {
       await timelineEngine.autoLoadDefaultProject()
 
       expect(global.fetch).toHaveBeenCalledWith('binect/project.json')
+      expect(global.fetch).toHaveBeenCalledWith('my-project/project.json')
       expect(global.fetch).toHaveBeenCalledWith('example/project.json')
     })