add test case with empty overrides and env variables being set

Author: Anmol1696

packages/smtppostmaster/__tests__/send.test.ts

@@ -2,11 +2,15 @@ import { send, resetTransport } from '../src/index';
 import { createSmtpCatcher } from './smtp-catcher';
 
 describe('send', () => {
+  const originalEnv = { ...process.env };
+
   afterEach(() => {
     resetTransport();
+    // Restore original env vars
+    process.env = { ...originalEnv };
   });
 
-  it('sends email via SMTP catcher', async () => {
+  it('sends email via SMTP catcher with overrides', async () => {
     const catcher = await createSmtpCatcher();
 
     try {
@@ -33,4 +37,34 @@ describe('send', () => {
       await catcher.stop();
     }
   }, 10000);
+
+  it('sends email using SMTP config from environment variables', async () => {
+    const catcher = await createSmtpCatcher();
+
+    // Set SMTP config via environment variables
+    process.env.SMTP_HOST = catcher.host;
+    process.env.SMTP_PORT = String(catcher.port);
+    process.env.SMTP_SECURE = 'false';
+    process.env.SMTP_FROM = 'env-sender@example.com';
+
+    // Clear cached transport to pick up new env vars
+    resetTransport();
+
+    try {
+      // Send without overrides - should use env vars
+      await send({
+        to: 'recipient@example.com',
+        subject: 'Email from env config',
+        text: 'This email was sent using env var configuration.'
+      });
+
+      const message = await catcher.waitForMessage(5000);
+
+      expect(message.raw).toContain('Subject: Email from env config');
+      expect(message.raw).toContain('This email was sent using env var configuration.');
+      expect(message.raw).toContain('From: env-sender@example.com');
+    } finally {
+      await catcher.stop();
+    }
+  }, 10000);
 });