# D3 Tree Visualization - UAT Test Report

**Date**: December 9, 2025
**Tester**: Web QA Agent
**Test URL**: http://localhost:8080
**Status**: FAILED - Critical rendering issues identified

---

## Executive Summary

The D3 tree visualization is fundamentally broken due to a design flaw where **no connector lines are rendered in the initial view**. The root cause is that the code explicitly returns an empty array of links when in `tree_root` mode, treating the initial view as just a "list of folders" rather than a tree structure.

**Business Impact**:
- Users cannot understand the hierarchical structure of their codebase
- The visualization contradicts the D3 tree pattern expectations
- Navigation appears broken (clicking folders has no visible effect)

---

## Test Environment

- **Browser**: Safari (macOS)
- **Server**: mcp-vector-search visualization server at localhost:8080
- **Data**: Project codebase with 8,336 nodes and 14,758 links

---

## Test Results

### 1. Initial View Test ❌ FAILED

**Test**: Navigate to http://localhost:8080 and observe the initial visualization

**Expected Behavior**:
- Root folders displayed on the left side
- Hierarchical connections visible between parent and child nodes
- Curved connector lines showing relationships
- Tree structure clearly visible

**Actual Behavior**:
- 12 root nodes (folders and files) displayed vertically
- **ZERO connector lines rendered**
- No visible tree structure
- Nodes appear as a disconnected list

**Screenshots**:
![Initial View](/tmp/safari_viz_screen.png)

**Debug Data**:
```json
{
  "allNodesCount": 8336,
  "visibleNodesSize": 12,
  "stateManagerExists": true,
  "d3NodesCount": 12,
  "d3LinksCount": 0,
  "viewMode": "tree_root",
  "expansionPath": []
}
```

**Key Finding**: `d3LinksCount: 0` - No links are being rendered!

---

### 2. Node Click Test ❌ FAILED

**Test**: Click on the "src" folder to expand it

**Expected Behavior**:
- Folder expands to show children on the right
- Connector lines appear between parent and children
- Tree structure expands horizontally
- View mode transitions from `tree_root` to `tree_expanded`

**Actual Behavior**:
- Clicking has no visible effect
- View remains identical to initial state
- View mode stays as `tree_root`
- expansionPath remains empty

**Screenshots**:
![After Click](/tmp/safari_viz_after_click.png)

**Debug Data After Click**:
```json
{
  "viewMode": "tree_root",
  "expansionPath": [],
  "visibleNodesCount": 12,
  "d3NodesCount": 12,
  "d3LinksCount": 0
}
```

**Key Finding**: Click handlers are not functioning - state does not change.

---

### 3. Console Error Analysis ✅ NO JAVASCRIPT ERRORS

**Test**: Check browser console for JavaScript errors

**Result**: No JavaScript errors or warnings detected. The code is executing without exceptions.

**Console Log Summary**:
- Graph loads successfully
- State manager initializes properly
- D3.js library loads correctly
- All nodes render successfully
- Link filtering function executes without errors

**Key Finding**: The problem is NOT a JavaScript error - it's a design decision in the code.

---

## Root Cause Analysis

### Primary Issue: Links Explicitly Disabled in tree_root Mode

**File**: `/Users/masa/Projects/mcp-vector-search/src/mcp_vector_search/cli/commands/visualize/templates/scripts.py`
**Function**: `getFilteredLinksForCurrentViewV2()`
**Lines**: 3774-3777

```javascript
// No edges in tree_root mode (initial overview - just list of folders)
if (stateManager.viewMode === 'tree_root') {
    return [];
}
```

**Analysis**:
1. The code treats `tree_root` mode as a "list view" with no connections
2. This contradicts the D3 tree visualization pattern
3. Even though there are 14,758 links in `allLinks`, the filter returns 0 links
4. The function comment explicitly states this is intentional: "just list of folders"

**Debug Evidence**:
```json
{
  "allLinksCount": 14758,
  "filteredLinksCount": 0,
  "viewMode": "tree_root"
}
```

### Secondary Issue: Click Handlers Not Functioning

**Observation**: Clicking on nodes does not trigger expansion or state changes.

**Evidence**:
- State remains in `tree_root` mode after clicking
- expansionPath stays empty
- No visible changes in the visualization

**Hypothesis**: The click handler may not be properly attached to the rendered nodes, or there's a missing event listener binding.

---

## Link Types in Data

The codebase contains these link types:
- `dir_containment` - Directory contains file/directory
- `file_containment` - File contains code elements
- `dir_hierarchy` - Directory hierarchy relationships
- `caller` - Function/method call relationships

**Current Filtering Logic**:
- `tree_root` mode: Returns **0 links** (intentional)
- `tree_expanded` mode: Shows only containment edges
- `file_detail` mode: Shows only caller edges within a file

---

## Business Requirements Validation

### Requirement: "Tree structure should be visible like D3.js tree examples"

**Status**: ❌ NOT MET

**Expected**: Hierarchical tree with visible parent-child connections
**Actual**: Flat list with no connections

**Gap**: The initial view needs to show containment relationships between root nodes and their immediate children to establish the tree structure.

### Requirement: "Clicking folders should expand them to show children"

**Status**: ❌ NOT MET

**Expected**: Interactive expansion with visual feedback
**Actual**: No response to clicks

**Gap**: Click handlers are not properly wired up or state transitions are broken.

### Requirement: "Curved connector lines between nodes"

**Status**: ⚠️ PARTIALLY MET

**Expected**: D3 linkHorizontal curved paths
**Actual**: Link rendering code exists but returns 0 links

**Gap**: The link rendering code is correct, but the filtering logic prevents any links from being displayed.

---

## Recommendations

### Critical Priority

1. **Fix tree_root Mode Link Filtering**
   - Modify `getFilteredLinksForCurrentViewV2()` to show containment edges even in `tree_root` mode
   - Show at least one level of hierarchy (root → immediate children)
   - This will make the tree structure visible from the start

2. **Fix Node Click Handlers**
   - Verify `handleNodeClick` function is properly defined and attached
   - Ensure event listeners are bound to rendered nodes
   - Add debug logging to track click events

### High Priority

3. **Add Visual Feedback for Interactions**
   - Hover states on clickable nodes
   - Loading indicators during expansion
   - Clear visual distinction between collapsed and expanded nodes

4. **Improve Initial View**
   - Consider showing collapsed state indicators (chevrons, +/- icons)
   - Add tooltips explaining that nodes are clickable
   - Display a hint message: "Click folders to expand"

### Medium Priority

5. **Add Progressive Disclosure**
   - Phase 1: Show root nodes with immediate children (1 level deep)
   - Phase 2: Expand selected branches interactively
   - Phase 3: Show detailed code elements within files

6. **Add Testing**
   - Unit tests for link filtering logic
   - Integration tests for state transitions
   - E2E tests for user interaction flows

---

## Technical Findings

### D3.js Integration Status

**✅ Working**:
- D3.js library loads correctly (v7)
- SVG rendering works
- Node positioning calculated correctly
- Tree layout algorithm available

**❌ Broken**:
- Link data binding returns empty array
- Click event handling not triggering state changes
- Tree expansion mechanism not functioning

### State Management

**Current State**:
```javascript
viewMode: "tree_root"
expansionPath: []
visibleNodes: 12 (Set)
allNodes: 8336
allLinks: 14758
```

**Expected State After Click**:
```javascript
viewMode: "tree_expanded"
expansionPath: ["src_node_id"]
visibleNodes: 12+ (includes children)
```

### Performance Metrics

- Initial load: Fast (< 1 second)
- Node rendering: 12 nodes rendered successfully
- Link rendering: N/A (0 links)
- Memory: Within normal range
- No browser performance issues detected

---

## Screenshots Reference

1. **Initial View** - Shows 12 root nodes with no connections
2. **After Click** - Identical to initial view (no change)
3. **Console Debug** - Shows d3LinksCount: 0

All screenshots saved in `/tmp/safari_*.png`

---

## Comparison with Expected Behavior

### Reference: D3.js Tree Example (https://d3js.org/d3-hierarchy/tree)

**Expected Features**:
- Horizontal tree layout (root on left, children to the right)
- Curved connector lines between parent and child
- Interactive expansion (click node to collapse/expand)
- Smooth transitions during expansion
- Clear visual hierarchy

**Current Implementation**:
- ❌ No horizontal expansion (list layout only)
- ❌ No connector lines (links filtered out)
- ❌ No interactive expansion (clicks don't work)
- ✅ Smooth transitions (code exists but not visible)
- ❌ No visual hierarchy (flat list)

---

## Acceptance Criteria

### Must Have (Phase 1)
- [ ] Root nodes display with visible containment connections
- [ ] Clicking a folder expands it to show children
- [ ] Curved connector lines render between parent and children
- [ ] Tree structure is visually apparent from initial view

### Should Have (Phase 2)
- [ ] Progressive disclosure (click to expand deeper levels)
- [ ] Breadcrumb navigation showing current path
- [ ] Visual indicators for collapsed vs expanded nodes
- [ ] Hover states and tooltips

### Nice to Have (Phase 3)
- [ ] Zoom and pan controls
- [ ] Search/filter functionality
- [ ] Export visualization as image
- [ ] Performance optimization for large codebases

---

## Next Steps

1. **Immediate**: Fix link filtering to show containment edges in tree_root mode
2. **Urgent**: Debug and fix node click handlers
3. **Soon**: Add visual expansion indicators and user guidance
4. **Later**: Implement comprehensive testing suite

---

## Conclusion

The D3 tree visualization has a fundamental design flaw where the initial view is treated as a "list" rather than a "tree", resulting in zero visible connections between nodes. This contradicts user expectations and standard D3 tree patterns.

The fix requires:
1. Modifying the link filtering logic to show containment edges in tree_root mode
2. Fixing the click event handlers to enable interactive expansion
3. Adding visual feedback to guide user interactions

**Estimated Fix Effort**: 2-4 hours for core functionality, 4-8 hours for polish and testing.

---

**Report Generated**: December 9, 2025
**Tools Used**: Safari, AppleScript, JavaScript debugging
**Agent**: Web QA Agent v2.0
