test: Add comprehensive test suite for database functionality

- Add unit tests for database operations and optimization
- Test external data source loading and caching
- Add callsign manager functionality tests
- Create test helpers for database testing utilities
- Ensure database reliability and performance validation

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

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

internal/database/database_test.go

@@ -0,0 +1,167 @@
+package database
+
+import (
+	"os"
+	"testing"
+	"time"
+)
+
+func TestNewDatabase(t *testing.T) {
+	// Create temporary database file
+	tempFile, err := os.CreateTemp("", "test_skyview_*.db")
+	if err != nil {
+		t.Fatal("Failed to create temp database file:", err)
+	}
+	defer os.Remove(tempFile.Name())
+	tempFile.Close()
+
+	config := &Config{
+		Path:           tempFile.Name(),
+		VacuumInterval: time.Hour,
+	}
+
+	db, err := NewDatabase(config)
+	if err != nil {
+		t.Fatal("Failed to create database:", err)
+	}
+	defer db.Close()
+
+	if db == nil {
+		t.Fatal("NewDatabase() returned nil")
+	}
+
+	// Test connection
+	conn := db.GetConnection()
+	if conn == nil {
+		t.Fatal("GetConnection() returned nil")
+	}
+
+	// Test basic query
+	var result int
+	err = conn.QueryRow("SELECT 1").Scan(&result)
+	if err != nil {
+		t.Error("Basic query failed:", err)
+	}
+	if result != 1 {
+		t.Error("Basic query returned wrong result:", result)
+	}
+}
+
+func TestDatabaseClose(t *testing.T) {
+	tempFile, err := os.CreateTemp("", "test_skyview_*.db")
+	if err != nil {
+		t.Fatal("Failed to create temp database file:", err)
+	}
+	defer os.Remove(tempFile.Name())
+	tempFile.Close()
+
+	config := &Config{Path: tempFile.Name()}
+	db, err := NewDatabase(config)
+	if err != nil {
+		t.Fatal("Failed to create database:", err)
+	}
+
+	// Close should not error
+	if err := db.Close(); err != nil {
+		t.Error("Database Close() returned error:", err)
+	}
+
+	// Second close should be safe
+	if err := db.Close(); err != nil {
+		t.Error("Second Close() returned error:", err)
+	}
+
+	// Connection should be nil after close
+	conn := db.GetConnection()
+	if conn != nil {
+		t.Error("GetConnection() should return nil after Close()")
+	}
+}
+
+func TestDatabaseConfig(t *testing.T) {
+	tempFile, err := os.CreateTemp("", "test_skyview_*.db")
+	if err != nil {
+		t.Fatal("Failed to create temp database file:", err)
+	}
+	defer os.Remove(tempFile.Name())
+	tempFile.Close()
+
+	config := &Config{
+		Path:           tempFile.Name(),
+		VacuumInterval: 2 * time.Hour,
+	}
+
+	db, err := NewDatabase(config)
+	if err != nil {
+		t.Fatal("Failed to create database:", err)
+	}
+	defer db.Close()
+
+	// Test that config is stored correctly
+	if db.config != config {
+		t.Error("Database config not stored correctly")
+	}
+	if db.config.VacuumInterval != 2*time.Hour {
+		t.Error("VacuumInterval not preserved:", db.config.VacuumInterval)
+	}
+}
+
+func TestDatabaseMigrations(t *testing.T) {
+	db, cleanup := setupTestDatabase(t)
+	defer cleanup()
+
+	conn := db.GetConnection()
+
+	// Check that essential tables exist after migrations
+	tables := []string{"airlines", "airports", "callsign_cache", "data_sources", "aircraft_history"}
+	for _, table := range tables {
+		var count int
+		query := "SELECT COUNT(*) FROM sqlite_master WHERE type='table' AND name=?"
+		err := conn.QueryRow(query, table).Scan(&count)
+		if err != nil {
+			t.Errorf("Failed to check for table %s: %v", table, err)
+		}
+		if count != 1 {
+			t.Errorf("Table %s does not exist", table)
+		}
+	}
+}
+
+func TestDatabasePragmas(t *testing.T) {
+	tempFile, err := os.CreateTemp("", "test_skyview_*.db")
+	if err != nil {
+		t.Fatal("Failed to create temp database file:", err)
+	}
+	defer os.Remove(tempFile.Name())
+	tempFile.Close()
+
+	config := &Config{Path: tempFile.Name()}
+	db, err := NewDatabase(config)
+	if err != nil {
+		t.Fatal("Failed to create database:", err)
+	}
+	defer db.Close()
+
+	conn := db.GetConnection()
+
+	// Check that foreign keys are enabled
+	var foreignKeys int
+	err = conn.QueryRow("PRAGMA foreign_keys").Scan(&foreignKeys)
+	if err != nil {
+		t.Error("Failed to check foreign_keys pragma:", err)
+	}
+	if foreignKeys != 1 {
+		t.Error("Foreign keys should be enabled")
+	}
+
+	// Check journal mode
+	var journalMode string
+	err = conn.QueryRow("PRAGMA journal_mode").Scan(&journalMode)
+	if err != nil {
+		t.Error("Failed to check journal_mode:", err)
+	}
+	// Should be WAL mode for better concurrency
+	if journalMode != "wal" {
+		t.Errorf("Expected WAL journal mode, got: %s", journalMode)
+	}
+}