test: Add unit tests for NUMA distance relationship creation

[jra3]

Summary

The createNUMADistanceRelationship function has 0% test coverage despite being critical for NUMA topology modeling and performance optimization.

Background

NUMA distance relationships are essential for:

• Performance-aware workload scheduling
• Memory locality optimization
• Multi-socket server topology understanding
• Cloud instance NUMA configuration validation

Missing Test Coverage

Function with 0% Coverage:

• createNUMADistanceRelationship - 0% coverage (complete gap)

NUMA Distance Relationship Logic

The function creates relationships between NUMA nodes with distance metrics:

func (b *Builder) createNUMADistanceRelationship(
    fromNode, toNode *resourcev1.ResourceRef, 
    fromNodeID, toNodeID, distance int32
) error

Required Test Scenarios

1. Basic Distance Relationship Creation

func TestCreateNUMADistanceRelationship_Basic(t *testing.T) {
    // Test creating distance relationship between two NUMA nodes
    // Test bidirectional relationship creation
    // Test distance value preservation
}

2. NUMA Distance Values

func TestCreateNUMADistanceRelationship_DistanceValues(t *testing.T) {
    tests := []struct {
        name      string
        distance  int32
        expectErr bool
    }{
        {"local_node", 10, false},      // Same node (typical local distance)
        {"remote_node", 20, false},     // Remote node (typical remote distance)
        {"far_node", 40, false},        // Far node (multi-hop)
        {"zero_distance", 0, false},    // Edge case: zero distance
        {"high_distance", 255, false},  // Edge case: maximum distance
    }
}

3. Resource Reference Validation

func TestCreateNUMADistanceRelationship_Validation(t *testing.T) {
    // Test nil fromNode reference
    // Test nil toNode reference
    // Test invalid node IDs
    // Test self-referential relationships
}

4. Predicate Creation

func TestCreateNUMADistanceRelationship_Predicate(t *testing.T) {
    // Test NumaDistancePredicate creation
    // Test predicate marshaling to protobuf
    // Test predicate field population
}

5. Store Integration

func TestCreateNUMADistanceRelationship_Store(t *testing.T) {
    // Test successful relationship storage
    // Test store failure handling
    // Test duplicate relationship handling
}

6. Real NUMA Topology Scenarios

func TestCreateNUMADistanceRelationship_RealTopologies(t *testing.T) {
    // Single-socket system (node 0 only)
    // Dual-socket system (nodes 0,1 with typical distances)
    // Quad-socket system (nodes 0,1,2,3 with distance matrix)
    // AMD EPYC systems (different distance patterns)
    // Intel Xeon systems (different distance patterns)
}

NUMA Distance Matrix Examples

Typical Dual-Socket Server:

Node  0    1
0     10   20
1     20   10

Typical Quad-Socket Server:

Node  0    1    2    3
0     10   20   20   40
1     20   10   40   20
2     20   40   10   20
3     40   20   20   10

Implementation Plan

Phase 1: Basic Functionality

• Test basic relationship creation
• Test predicate marshaling
• Test store integration

Phase 2: Validation & Error Handling

• Test input validation
• Test error scenarios
• Test edge cases (zero/max distances)

Phase 3: Real-World Scenarios

• Test common NUMA topologies
• Test different server architectures
• Validate distance matrix patterns

Success Criteria

• Achieve 100% coverage for createNUMADistanceRelationship
• Test all NUMA distance scenarios
• Validate proper predicate creation
• Test error handling and edge cases
• Cover real-world NUMA topologies

Priority

MEDIUM - Critical for NUMA-aware performance but affects specific server configurations.

Related

• Issue test: Add comprehensive unit tests for hardware manager lifecycle #159 (Hardware Manager testing)
• NUMA topology accuracy for performance optimization
• Multi-socket server support validation