store test [nfc]: Pull out prepare-error helpers

This lets us share this setup code between the tests of how the logic
responds (retry, reload, or otherwise) and how it reports errors to
the user (or doesn't), while keeping separate test cases so that test
failures of one kind don't obscure the story with the other.

Author: gnprice

test/model/store_test.dart

@@ -671,30 +671,6 @@ void main() {
       });
     }
 
-    test('expired queue disposes registered MessageListView instances', () => awaitFakeAsync((async) async {
-      // Regression test for: https://github.com/zulip/zulip-flutter/issues/810
-      await preparePoll();
-
-      // Make sure there are [MessageListView]s in the message store.
-      MessageListView.init(store: store, narrow: const MentionsNarrow());
-      MessageListView.init(store: store, narrow: const StarredMessagesNarrow());
-      check(store.debugMessageListViews).length.equals(2);
-
-      // Let the server expire the event queue.
-      connection.prepare(httpStatus: 400, json: {
-        'result': 'error', 'code': 'BAD_EVENT_QUEUE_ID',
-        'queue_id': updateMachine.queueId,
-        'msg': 'Bad event queue ID: ${updateMachine.queueId}',
-      });
-      updateMachine.debugAdvanceLoop();
-      async.flushMicrotasks();
-      await Future<void>.delayed(Duration.zero);
-
-      // The old store's [MessageListView]s have been disposed.
-      // (And no exception was thrown; that was #810.)
-      check(store.debugMessageListViews).isEmpty();
-    }));
-
     void checkRetry(void Function() prepareError) {
       awaitFakeAsync((async) async {
         await preparePoll(lastEventId: 1);
@@ -727,31 +703,75 @@ void main() {
 
     // These cases are ordered by how far the request got before it failed.
 
+    void prepareNetworkExceptionSocketException() {
+      connection.prepare(exception: const SocketException('failed'));
+    }
+
+    void prepareNetworkException() {
+      connection.prepare(exception: Exception("failed"));
+    }
+
+    void prepareServer5xxException() {
+      connection.prepare(httpStatus: 500, body: 'splat');
+    }
+
+    void prepareMalformedServerResponseException() {
+      connection.prepare(httpStatus: 200, body: 'nonsense');
+    }
+
+    void prepareZulipApiExceptionBadRequest() {
+      connection.prepare(httpStatus: 400, json: {
+        'result': 'error', 'code': 'BAD_REQUEST', 'msg': 'Bad request'});
+    }
+
+    void prepareExpiredEventQueue() {
+      connection.prepare(httpStatus: 400, json: {
+        'result': 'error', 'code': 'BAD_EVENT_QUEUE_ID',
+        'queue_id': updateMachine.queueId,
+        'msg': 'Bad event queue ID: ${updateMachine.queueId}',
+      });
+    }
+
     test('retries on NetworkException', () {
-      checkRetry(() => connection.prepare(exception: Exception("failed")));
+      checkRetry(prepareNetworkException);
     });
 
     test('retries on Server5xxException', () {
-      checkRetry(() => connection.prepare(httpStatus: 500, body: 'splat'));
+      checkRetry(prepareServer5xxException);
     });
 
     test('retries on MalformedServerResponseException', () {
-      checkRetry(() => connection.prepare(httpStatus: 200, body: 'nonsense'));
+      checkRetry(prepareMalformedServerResponseException);
     });
 
     test('retries on generic ZulipApiException', () {
-      checkRetry(() => connection.prepare(httpStatus: 400, json: {
-        'result': 'error', 'code': 'BAD_REQUEST', 'msg': 'Bad request'}));
+      checkRetry(prepareZulipApiExceptionBadRequest);
     });
 
     test('reloads on expired queue', () {
-      checkReload(() => connection.prepare(httpStatus: 400, json: {
-        'result': 'error', 'code': 'BAD_EVENT_QUEUE_ID',
-        'queue_id': updateMachine.queueId,
-        'msg': 'Bad event queue ID: ${updateMachine.queueId}',
-      }));
+      checkReload(prepareExpiredEventQueue);
     });
 
+    test('expired queue disposes registered MessageListView instances', () => awaitFakeAsync((async) async {
+      // Regression test for: https://github.com/zulip/zulip-flutter/issues/810
+      await preparePoll();
+
+      // Make sure there are [MessageListView]s in the message store.
+      MessageListView.init(store: store, narrow: const MentionsNarrow());
+      MessageListView.init(store: store, narrow: const StarredMessagesNarrow());
+      check(store.debugMessageListViews).length.equals(2);
+
+      // Let the server expire the event queue.
+      prepareExpiredEventQueue();
+      updateMachine.debugAdvanceLoop();
+      async.flushMicrotasks();
+      await Future<void>.delayed(Duration.zero);
+
+      // The old store's [MessageListView]s have been disposed.
+      // (And no exception was thrown; that was #810.)
+      check(store.debugMessageListViews).isEmpty();
+    }));
+
     group('report error', () {
       String? lastReportedError;
       String? takeLastReportedError() {
@@ -781,8 +801,7 @@ void main() {
       test('report non-transient errors', () => awaitFakeAsync((async) async {
         await prepare();
 
-        connection.prepare(httpStatus: 400, json: {
-          'result': 'error', 'code': 'BAD_REQUEST', 'msg': 'Bad request'});
+        prepareZulipApiExceptionBadRequest();
         pollAndFail(async);
         check(takeLastReportedError()).isNotNull().startsWith(
           "Error connecting to Zulip. Retrying…\n"
@@ -794,14 +813,14 @@ void main() {
 
         // There should be no user visible error messages during these retries.
         for (int i = 0; i < UpdateMachine.transientFailureCountNotifyThreshold; i++) {
-          connection.prepare(httpStatus: 500, body: 'splat');
+          prepareServer5xxException();
           pollAndFail(async);
           check(takeLastReportedError()).isNull();
           // This skips the pending polling backoff.
           async.flushTimers();
         }
 
-        connection.prepare(httpStatus: 500, body: 'splat');
+        prepareServer5xxException();
         pollAndFail(async);
         check(takeLastReportedError()).isNotNull().startsWith(
           "Error connecting to Zulip. Retrying…\n"
@@ -812,14 +831,14 @@ void main() {
         await prepare();
 
         for (int i = 0; i < UpdateMachine.transientFailureCountNotifyThreshold; i++) {
-          connection.prepare(exception: const SocketException('failed'));
+          prepareNetworkExceptionSocketException();
           pollAndFail(async);
           check(takeLastReportedError()).isNull();
           // This skips the pending polling backoff.
           async.flushTimers();
         }
 
-        connection.prepare(exception: const SocketException('failed'));
+        prepareNetworkExceptionSocketException();
         pollAndFail(async);
         // Normally we start showing user visible error messages for transient
         // errors after enough number of retries.