Added validation when task type, category, signatories and action taken are empty upon completing a task

test/tasks_provider_test.dart

@@ -90,8 +90,8 @@ void main() {
       // note: controller expects SupabaseClient; using dynamic bypass.
     });
 
-    test('cannot complete a task without request details', () async {
-      // insert a task with no metadata
+    test('cannot complete a task without required metadata', () async {
+      // insert a task with no metadata at all
       final row = {'id': 'tsk-1', 'status': 'queued'};
       fake.tables['tasks']!.add(row);
 
@@ -101,6 +101,43 @@ void main() {
       );
     });
 
+    test('cannot complete when signatories or action taken missing', () async {
+      // insert a task that has the basic request metadata but nothing else
+      final row = {
+        'id': 'tsk-3',
+        'status': 'queued',
+        'request_type': 'Repair',
+        'request_category': 'Hardware',
+      };
+      fake.tables['tasks']!.add(row);
+
+      // still missing signatories/actionTaken
+      expect(
+        () => controller.updateTaskStatus(taskId: 'tsk-3', status: 'completed'),
+        throwsA(isA<Exception>()),
+      );
+
+      // add signatories but actionTaken still missing
+      await controller.updateTask(
+        taskId: 'tsk-3',
+        requestedBy: 'Alice',
+        notedBy: 'Bob',
+        receivedBy: 'Carol',
+      );
+      expect(
+        () => controller.updateTaskStatus(taskId: 'tsk-3', status: 'completed'),
+        throwsA(isA<Exception>()),
+      );
+
+      // add action taken (empty JSON string)
+      await controller.updateTask(taskId: 'tsk-3', actionTaken: '{}');
+      await controller.updateTaskStatus(taskId: 'tsk-3', status: 'completed');
+      expect(
+        fake.tables['tasks']!.firstWhere((t) => t['id'] == 'tsk-3')['status'],
+        'completed',
+      );
+    });
+
     test('completing after adding metadata succeeds', () async {
       // insert a task
       final row = {'id': 'tsk-2', 'status': 'queued'};