diff --git a/comid/macaddr_test.go b/comid/macaddr_test.go
new file mode 100644
index 00000000..7b7c60ce
--- /dev/null
+++ b/comid/macaddr_test.go
@@ -0,0 +1,99 @@
+package comid
+
+import (
+	"bytes"
+	"encoding/json"
+	"net"
+	"testing"
+)
+
+func TestMACaddr_UnmarshalJSON(t *testing.T) {
+	tests := []struct {
+		name       string
+		input      string
+		expected   MACaddr
+		shouldFail bool
+	}{
+		{
+			name:     "Valid MAC-48 with colon",
+			input:    `"00:00:5e:00:53:01"`,
+			expected: MACaddr(net.HardwareAddr{0x00, 0x00, 0x5e, 0x00, 0x53, 0x01}),
+		},
+		{
+			name:     "Valid MAC-48 with dash",
+			input:    `"00-00-5e-00-53-01"`,
+			expected: MACaddr(net.HardwareAddr{0x00, 0x00, 0x5e, 0x00, 0x53, 0x01}),
+		},
+		{
+			name:     "Valid EUI-64 with colon",
+			input:    `"02:00:5e:10:00:00:00:01"`,
+			expected: MACaddr(net.HardwareAddr{0x02, 0x00, 0x5e, 0x10, 0x00, 0x00, 0x00, 0x01}),
+		},
+		{
+			name:     "Valid EUI-64 with dash",
+			input:    `"02-00-5e-10-00-00-00-01"`,
+			expected: MACaddr(net.HardwareAddr{0x02, 0x00, 0x5e, 0x10, 0x00, 0x00, 0x00, 0x01}),
+		},
+		{
+			name:       "Invalid MAC address format",
+			input:      `"invalid-mac"`,
+			shouldFail: true,
+		},
+		{
+			name:       "Invalid JSON type",
+			input:      `12345`,
+			shouldFail: true,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			var mac MACaddr
+			err := json.Unmarshal([]byte(test.input), &mac)
+			if test.shouldFail {
+				if err == nil {
+					t.Errorf("expected failure but got no error")
+				}
+			} else {
+				if err != nil {
+					t.Errorf("unexpected error: %v", err)
+				}
+				// Compare the MAC address slices using bytes.Equal
+				if !bytes.Equal([]byte(mac), []byte(test.expected)) {
+					t.Errorf("expected %v, got %v", test.expected, mac)
+				}
+			}
+		})
+	}
+}
+
+func TestMACaddr_MarshalJSON(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    MACaddr
+		expected string
+	}{
+		{
+			name:     "Valid MAC-48",
+			input:    MACaddr(net.HardwareAddr{0x00, 0x00, 0x5e, 0x00, 0x53, 0x01}),
+			expected: `"00:00:5e:00:53:01"`,
+		},
+		{
+			name:     "Valid EUI-64",
+			input:    MACaddr(net.HardwareAddr{0x02, 0x00, 0x5e, 0x10, 0x00, 0x00, 0x00, 0x01}),
+			expected: `"02:00:5e:10:00:00:00:01"`,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			data, err := json.Marshal(test.input)
+			if err != nil {
+				t.Errorf("unexpected error: %v", err)
+			}
+			if string(data) != test.expected {
+				t.Errorf("expected %s, got %s", test.expected, string(data))
+			}
+		})
+	}
+}