test(TripMonitorNotification): Add test file for sort order.

src/test/java/org/opentripplanner/middleware/models/TripMonitorNotificationTest.java

@@ -0,0 +1,34 @@
+package org.opentripplanner.middleware.models;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+
+import org.junit.jupiter.api.Test;
+import org.opentripplanner.middleware.tripmonitor.jobs.NotificationType;
+
+import java.util.Comparator;
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+class TripMonitorNotificationTest {
+    @Test
+    void testSortOrderPutsInitialReminderFirst() {
+        TripMonitorNotification reminder = new TripMonitorNotification(NotificationType.INITIAL_REMINDER, "reminder");
+        Set<TripMonitorNotification> notifications = Set.of(
+            new TripMonitorNotification(NotificationType.ALERT_FOUND, "alert"),
+            new TripMonitorNotification(NotificationType.DEPARTURE_DELAY, "departure delay"),
+            reminder,
+            new TripMonitorNotification(NotificationType.ARRIVAL_DELAY, "arrival delay")
+        );
+
+        List<TripMonitorNotification> sortedNotifications = notifications.stream()
+            .sorted(Comparator.comparingInt(TripMonitorNotification::sortOrder))
+            .collect(Collectors.toList());
+
+        assertEquals(reminder, sortedNotifications.get(0));
+        for (int i = 1; i < sortedNotifications.size(); i++) {
+            assertNotEquals(reminder, sortedNotifications.get(i));
+        }
+    }
+}