add PHPUnit test for RelaySet

tests/RelaySetTest.php

@@ -0,0 +1,44 @@
+<?php
+
+declare(strict_types=1);
+
+use PHPUnit\Framework\TestCase;
+use swentel\nostr\Event\Event;
+use swentel\nostr\Key\Key;
+use swentel\nostr\Relay\Relay;
+use swentel\nostr\Relay\RelaySet;
+use swentel\nostr\Relay\CommandResult;
+use swentel\nostr\Sign\Sign;
+
+class RelaySetTest extends TestCase
+{
+    /**
+     * Tests sending a note to a set of relays.
+     */
+    public function testSendNoteToRelaySet()
+    {
+        $keys = new Key();
+        $private_key = $keys->generatePrivateKey();
+
+        $note = new Event();
+        $note->setContent('Hello world');
+
+        $signer = new Sign();
+        $signer->signEvent($note, $private_key);
+
+        $relay1 = new Relay('wss://example1.com');
+        $relay2 = new Relay('wss://example2.com');
+        $relay3 = new Relay('wss://example3.com');
+
+        $relaySet = $this->createMock(RelaySet::class);
+        $relaySet->setRelays([$relay1, $relay2, $relay3]);
+        $relaySet->expects($this->once())
+            ->method('send')
+            ->willReturn(new CommandResult(['OK', $note->getId(), true, '']));
+
+        $response = $relaySet->send();
+        $this->assertTrue(
+            $response->isSuccess(),
+        );
+    }
+}