test(handler): add unit tests for SOCKS5 networkAddr helper

Add 8-case table-driven test covering nil addr, IPv4/IPv6/domain/unknown
addr types for both tcp and udp networks.

Ref: 03f4b12 (fix(handler): use addr-family-specific network for SOCKS5 BIND)

handler/socks/v5/network_test.go

@@ -0,0 +1,68 @@
+package v5
+
+import (
+	"testing"
+
+	"github.com/go-gost/gosocks5"
+)
+
+func TestNetworkAddr(t *testing.T) {
+	tests := []struct {
+		name    string
+		network string
+		addr    *gosocks5.Addr
+		want    string
+	}{
+		{
+			name:    "nil addr returns unmodified",
+			network: "tcp",
+			addr:    nil,
+			want:    "tcp",
+		},
+		{
+			name:    "IPv4 tcp returns tcp4",
+			network: "tcp",
+			addr:    &gosocks5.Addr{Type: gosocks5.AddrIPv4},
+			want:    "tcp4",
+		},
+		{
+			name:    "IPv6 tcp returns tcp6",
+			network: "tcp",
+			addr:    &gosocks5.Addr{Type: gosocks5.AddrIPv6},
+			want:    "tcp6",
+		},
+		{
+			name:    "IPv4 udp returns udp4",
+			network: "udp",
+			addr:    &gosocks5.Addr{Type: gosocks5.AddrIPv4},
+			want:    "udp4",
+		},
+		{
+			name:    "IPv6 udp returns udp6",
+			network: "udp",
+			addr:    &gosocks5.Addr{Type: gosocks5.AddrIPv6},
+			want:    "udp6",
+		},
+		{
+			name:    "domain addr returns unmodified",
+			network: "tcp",
+			addr:    &gosocks5.Addr{Type: gosocks5.AddrDomain},
+			want:    "tcp",
+		},
+		{
+			name:    "unknown addr type returns unmodified",
+			network: "udp",
+			addr:    &gosocks5.Addr{Type: 99},
+			want:    "udp",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := networkAddr(tt.network, tt.addr)
+			if got != tt.want {
+				t.Errorf("networkAddr(%q, %v) = %q, want %q", tt.network, tt.addr, got, tt.want)
+			}
+		})
+	}
+}