refactor tests for new constructor pattern

test/unified-margin/private.write.test.ts

@@ -1,7 +1,6 @@
 import { API_ERROR_CODE, UnifiedMarginClient } from '../../src';
 
 describe('Private Unified Margin REST API POST Endpoints', () => {
-  const useLivenet = true;
   const API_KEY = process.env.API_KEY_COM;
   const API_SECRET = process.env.API_SECRET_COM;
 
@@ -10,7 +9,11 @@ describe('Private Unified Margin REST API POST Endpoints', () => {
     expect(API_SECRET).toStrictEqual(expect.any(String));
   });
 
-  const api = new UnifiedMarginClient(API_KEY, API_SECRET, useLivenet);
+  const api = new UnifiedMarginClient({
+    key: API_KEY,
+    secret: API_SECRET,
+    testnet: false,
+  });
 
   const symbol = 'BTCUSDT';
   const category = 'linear';