diff --git a/rsscloud/send-post-notifications.php b/rsscloud/send-post-notifications.php
index d8d2611..3bc9781 100644
--- a/rsscloud/send-post-notifications.php
+++ b/rsscloud/send-post-notifications.php
@@ -18,6 +18,10 @@ function rsscloud_send_post_notifications( $rss2_url = false ) {
 		$notify = array();
 	}
 
+	if ( ! isset( $notify[ $rss2_url ] ) ) {
+		return;
+	}
+
 	$need_update = false;
 	foreach ( $notify[ $rss2_url ] as $notify_url => $n ) {
 		if ( 'active' !== $n['status'] ) {
diff --git a/tests/test-send-post-notifications.php b/tests/test-send-post-notifications.php
new file mode 100644
index 0000000..62115b0
--- /dev/null
+++ b/tests/test-send-post-notifications.php
@@ -0,0 +1,277 @@
+<?php
+/**
+ * Tests for send-post-notifications functions.
+ *
+ * @package Rsscloud
+ */
+
+class SendPostNotificationsTest extends WP_UnitTestCase {
+
+	private $feed_url = 'http://example.org/?feed=rss2';
+
+	private $http_requests = array();
+
+	public function set_up() {
+		parent::set_up();
+		$this->http_requests = array();
+	}
+
+	private function set_notifications( $data ) {
+		rsscloud_update_hub_notifications( $data );
+	}
+
+	private function build_notifications( $overrides = array() ) {
+		$notify_url = isset( $overrides['notify_url'] ) ? $overrides['notify_url'] : 'http://subscriber.example.com:80/rpc';
+
+		return array(
+			$this->feed_url => array(
+				$notify_url => array(
+					'protocol'      => isset( $overrides['protocol'] ) ? $overrides['protocol'] : 'http-post',
+					'status'        => isset( $overrides['status'] ) ? $overrides['status'] : 'active',
+					'failure_count' => isset( $overrides['failure_count'] ) ? $overrides['failure_count'] : 0,
+				),
+			),
+		);
+	}
+
+	private function mock_http_response( $status_code = 200 ) {
+		add_filter(
+			'pre_http_request',
+			function ( $preempt, $args, $url ) use ( $status_code ) {
+				$this->http_requests[] = array(
+					'url'  => $url,
+					'args' => $args,
+				);
+				return array(
+					'response' => array(
+						'code'    => $status_code,
+						'message' => 'OK',
+					),
+					'body'     => '',
+				);
+			},
+			10,
+			3
+		);
+	}
+
+	private function mock_http_error() {
+		add_filter(
+			'pre_http_request',
+			function ( $preempt, $args, $url ) {
+				$this->http_requests[] = array(
+					'url'  => $url,
+					'args' => $args,
+				);
+				return new WP_Error( 'http_request_failed', 'Connection refused' );
+			},
+			10,
+			3
+		);
+	}
+
+	public function test_successful_notification_sends_post_request() {
+		$this->set_notifications( $this->build_notifications() );
+		$this->mock_http_response( 200 );
+
+		rsscloud_send_post_notifications( $this->feed_url );
+
+		$this->assertCount( 1, $this->http_requests );
+		$this->assertSame( 'http://subscriber.example.com:80/rpc', $this->http_requests[0]['url'] );
+		$this->assertSame( 'POST', $this->http_requests[0]['args']['method'] );
+		$this->assertSame( $this->feed_url, $this->http_requests[0]['args']['body']['url'] );
+	}
+
+	public function test_successful_notification_does_not_update_storage() {
+		$notifications = $this->build_notifications();
+		$this->set_notifications( $notifications );
+		$this->mock_http_response( 200 );
+
+		rsscloud_send_post_notifications( $this->feed_url );
+
+		$this->assertSame( $notifications, rsscloud_get_hub_notifications() );
+	}
+
+	public function test_http_error_increments_failure_count() {
+		$this->set_notifications( $this->build_notifications() );
+		$this->mock_http_error();
+
+		rsscloud_send_post_notifications( $this->feed_url );
+
+		$notify = rsscloud_get_hub_notifications();
+		$this->assertSame( 1, $notify[ $this->feed_url ]['http://subscriber.example.com:80/rpc']['failure_count'] );
+	}
+
+	public function test_http_status_error_increments_failure_count() {
+		$this->set_notifications( $this->build_notifications() );
+		$this->mock_http_response( 500 );
+
+		rsscloud_send_post_notifications( $this->feed_url );
+
+		$notify = rsscloud_get_hub_notifications();
+		$this->assertSame( 1, $notify[ $this->feed_url ]['http://subscriber.example.com:80/rpc']['failure_count'] );
+	}
+
+	public function test_exceeding_max_failures_suspends_subscription() {
+		$this->set_notifications(
+			$this->build_notifications( array( 'failure_count' => RSSCLOUD_MAX_FAILURES ) )
+		);
+		$this->mock_http_error();
+
+		rsscloud_send_post_notifications( $this->feed_url );
+
+		$notify = rsscloud_get_hub_notifications();
+		$sub    = $notify[ $this->feed_url ]['http://subscriber.example.com:80/rpc'];
+		$this->assertSame( 'suspended', $sub['status'] );
+		$this->assertSame( RSSCLOUD_MAX_FAILURES + 1, $sub['failure_count'] );
+	}
+
+	public function test_successful_response_resets_failure_count() {
+		$this->set_notifications(
+			$this->build_notifications( array( 'failure_count' => 3 ) )
+		);
+		$this->mock_http_response( 200 );
+
+		rsscloud_send_post_notifications( $this->feed_url );
+
+		$notify = rsscloud_get_hub_notifications();
+		$this->assertSame( 0, $notify[ $this->feed_url ]['http://subscriber.example.com:80/rpc']['failure_count'] );
+	}
+
+	public function test_suspended_subscription_is_skipped() {
+		$this->set_notifications(
+			$this->build_notifications( array( 'status' => 'suspended' ) )
+		);
+		$this->mock_http_response( 200 );
+
+		rsscloud_send_post_notifications( $this->feed_url );
+
+		$this->assertCount( 0, $this->http_requests );
+	}
+
+	public function test_non_http_post_protocol_is_skipped() {
+		$this->set_notifications(
+			$this->build_notifications( array( 'protocol' => 'xml-rpc' ) )
+		);
+		$this->mock_http_response( 200 );
+
+		rsscloud_send_post_notifications( $this->feed_url );
+
+		$this->assertCount( 0, $this->http_requests );
+	}
+
+	public function test_no_subscriptions_does_not_error() {
+		$this->set_notifications( array() );
+		$this->mock_http_response( 200 );
+
+		// Should not produce any errors or warnings.
+		rsscloud_send_post_notifications( $this->feed_url );
+
+		$this->assertCount( 0, $this->http_requests );
+	}
+
+	public function test_uses_custom_port_from_notify_url() {
+		$this->set_notifications(
+			$this->build_notifications( array( 'notify_url' => 'http://subscriber.example.com:8080/rpc' ) )
+		);
+		$this->mock_http_response( 200 );
+
+		rsscloud_send_post_notifications( $this->feed_url );
+
+		$this->assertSame( 8080, $this->http_requests[0]['args']['port'] );
+	}
+
+	public function test_defaults_to_port_80_when_not_in_url() {
+		$this->set_notifications(
+			$this->build_notifications( array( 'notify_url' => 'http://subscriber.example.com/rpc' ) )
+		);
+		$this->mock_http_response( 200 );
+
+		rsscloud_send_post_notifications( $this->feed_url );
+
+		$this->assertSame( 80, $this->http_requests[0]['args']['port'] );
+	}
+
+	public function test_fires_feed_notifications_action() {
+		$this->set_notifications( array() );
+		$fired = false;
+		add_action(
+			'rsscloud_feed_notifications',
+			function ( $url ) use ( &$fired ) {
+				$fired = $url;
+			}
+		);
+
+		rsscloud_send_post_notifications( $this->feed_url );
+
+		$this->assertSame( $this->feed_url, $fired );
+	}
+
+	public function test_fires_send_notification_action_on_post() {
+		$this->set_notifications( $this->build_notifications() );
+		$this->mock_http_response( 200 );
+		$fired = false;
+		add_action(
+			'rsscloud_send_notification',
+			function () use ( &$fired ) {
+				$fired = true;
+			}
+		);
+
+		rsscloud_send_post_notifications( $this->feed_url );
+
+		$this->assertTrue( $fired );
+	}
+
+	public function test_fires_notify_failure_action_on_error() {
+		$this->set_notifications( $this->build_notifications() );
+		$this->mock_http_error();
+		$fired = false;
+		add_action(
+			'rsscloud_notify_failure',
+			function () use ( &$fired ) {
+				$fired = true;
+			}
+		);
+
+		rsscloud_send_post_notifications( $this->feed_url );
+
+		$this->assertTrue( $fired );
+	}
+
+	public function test_fires_suspend_action_when_max_failures_exceeded() {
+		$this->set_notifications(
+			$this->build_notifications( array( 'failure_count' => RSSCLOUD_MAX_FAILURES ) )
+		);
+		$this->mock_http_error();
+		$fired = false;
+		add_action(
+			'rsscloud_suspend_notification_url',
+			function () use ( &$fired ) {
+				$fired = true;
+			}
+		);
+
+		rsscloud_send_post_notifications( $this->feed_url );
+
+		$this->assertTrue( $fired );
+	}
+
+	public function test_fires_reset_failure_count_action_on_recovery() {
+		$this->set_notifications(
+			$this->build_notifications( array( 'failure_count' => 2 ) )
+		);
+		$this->mock_http_response( 200 );
+		$fired = false;
+		add_action(
+			'rsscloud_reset_failure_count',
+			function () use ( &$fired ) {
+				$fired = true;
+			}
+		);
+
+		rsscloud_send_post_notifications( $this->feed_url );
+
+		$this->assertTrue( $fired );
+	}
+}