Preserve C/H bits and extension bit

test/address.extensionbit.test.ts

@@ -0,0 +1,24 @@
+import { Address } from "../src/address";
+import { describe, it, expect } from "vitest";
+
+describe("Address extension handling", () => {
+  it("encodes and decodes extension", () => {
+    const addr = new Address("NOCALL", 7, false, 0b11, true);
+    const bytes = addr.toBytes();
+    expect((bytes[6] & 0x01)).toBe(1); // extension set
+    const decoded = Address.fromBytes(bytes);
+    expect(decoded.getExtension()).toBe(true);
+    expect(decoded.callsign).toBe("NOCALL");
+    expect(decoded.ssid).toBe(7);
+  });
+
+  it("can set and clear extension", () => {
+    const addr = new Address("TEST", 1);
+    addr.setExtension(true);
+    let bytes = addr.toBytes();
+    expect((bytes[6] & 0x01)).toBe(1);
+    addr.setExtension(false);
+    bytes = addr.toBytes();
+    expect((bytes[6] & 0x01)).toBe(0);
+  });
+});