add thread e2e tests

integration_test/helpers/fakes.dart

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+import "dart:async";
+
+import "package:app_links_platform_interface/app_links_platform_interface.dart";
+import "package:url_launcher_platform_interface/link.dart";
+import "package:url_launcher_platform_interface/url_launcher_platform_interface.dart";
+
+/// Delivers links to the app as if the OS had opened them.
+class FakeAppLinks extends AppLinksPlatform {
+  final _links = StreamController<Uri>.broadcast();
+
+  void open(Uri uri) => _links.add(uri);
+
+  @override
+  Future<Uri?> getInitialLink() async => null;
+
+  @override
+  Future<String?> getInitialLinkString() async => null;
+
+  @override
+  Future<Uri?> getLatestLink() async => null;
+
+  @override
+  Future<String?> getLatestLinkString() async => null;
+
+  @override
+  Stream<Uri> get uriLinkStream => _links.stream;
+
+  @override
+  Stream<String> get stringLinkStream =>
+      _links.stream.map((uri) => uri.toString());
+}
+
+/// Hands launched URLs to [onLaunch] instead of opening a browser.
+class FakeUrlLauncher(final void Function(Uri url) onLaunch)
+    extends UrlLauncherPlatform {
+  @override
+  LinkDelegate? get linkDelegate => null;
+
+  @override
+  Future<bool> canLaunch(String url) async => true;
+
+  @override
+  Future<bool> launchUrl(String url, LaunchOptions options) async {
+    onLaunch(.parse(url));
+    return true;
+  }
+}

integration_test/helpers/matrix_user.dart

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+import "dart:convert";
+
+import "package:fast_immutable_collections/fast_immutable_collections.dart";
+import "package:http/http.dart" as http;
+
+const homeserver = String.fromEnvironment("NEXUS_E2E_HOMESERVER");
+
+/// A user acting over the client-server API directly, as a control for the
+/// tests: it doesn't go through gomuks or any other Nexus code, so it sets
+/// things up and checks the server's side independently of what's being
+/// tested. That includes Nexus' models, so the JSON it sends is written out
+/// here rather than built the way Nexus builds it.
+class const MatrixUser(final String userId, final String accessToken) {
+  static Future<MatrixUser> login(String username, String password) async {
+    final json = await request(
+      "POST",
+      "/_matrix/client/v3/login",
+      body: {
+        "type": "m.login.password",
+        "identifier": {"type": "m.id.user", "user": username},
+        "password": password,
+      },
+    );
+    return MatrixUser(json["user_id"], json["access_token"]);
+  }
+
+  static Future<Map<String, dynamic>> request(
+    String method,
+    String path, {
+    String? accessToken,
+    Object? body,
+  }) async {
+    final httpRequest =
+        http.Request(method, Uri.parse(homeserver).resolve(path))
+          ..headers.addAll({
+            "Content-Type": "application/json",
+            if (accessToken != null) "Authorization": "Bearer $accessToken",
+          });
+    if (method != "GET") httpRequest.body = jsonEncode(body ?? {});
+    final response = await http.Response.fromStream(await httpRequest.send());
+
+    if (response.statusCode == 429) {
+      final retryAfter = jsonDecode(response.body)["retry_after_ms"] ?? 1000;
+      await Future.delayed(.new(milliseconds: retryAfter));
+      return request(method, path, accessToken: accessToken, body: body);
+    }
+    if (response.statusCode >= 300) {
+      throw StateError(
+        "$method $path failed with ${response.statusCode}: ${response.body}",
+      );
+    }
+    return jsonDecode(response.body);
+  }
+
+  Future<String> createRoom(String name) async => (await request(
+    "POST",
+    "/_matrix/client/v3/createRoom",
+    accessToken: accessToken,
+    body: {"name": name, "preset": "private_chat"},
+  ))["room_id"];
+
+  Future<void> invite(String roomId, String userId) => request(
+    "POST",
+    "/_matrix/client/v3/rooms/${Uri.encodeComponent(roomId)}/invite",
+    accessToken: accessToken,
+    body: {"user_id": userId},
+  );
+
+  Future<void> join(String roomId) => request(
+    "POST",
+    "/_matrix/client/v3/join/${Uri.encodeComponent(roomId)}",
+    accessToken: accessToken,
+  );
+
+  Future<void> logout() =>
+      request("POST", "/_matrix/client/v3/logout", accessToken: accessToken);
+
+  Future<String> sendEvent(
+    String roomId,
+    String type,
+    Map<String, Object> content,
+  ) async => (await request(
+    "PUT",
+    "/_matrix/client/v3/rooms/${Uri.encodeComponent(roomId)}/send/$type/"
+        "${DateTime.now().microsecondsSinceEpoch}",
+    accessToken: accessToken,
+    body: content,
+  ))["event_id"];
+
+  /// Sends a text message. With [threadRoot] it's a reply in that thread, and
+  /// otherwise with [replyTo] it's a reply to that event.
+  Future<String> send(
+    String roomId,
+    String body, {
+    String? threadRoot,
+    String? replyTo,
+  }) => sendEvent(roomId, "m.room.message", {
+    "msgtype": "m.text",
+    "body": body,
+    "m.relates_to": ?switch ((threadRoot, replyTo)) {
+      (final threadRoot?, _) => {
+        "rel_type": "m.thread",
+        "event_id": threadRoot,
+        "is_falling_back": true,
+        "m.in_reply_to": {"event_id": threadRoot},
+      },
+      (null, final replyTo?) => {
+        "m.in_reply_to": {"event_id": replyTo},
+      },
+      (null, null) => null,
+    },
+  });
+
+  /// Sends [rootBody], then [replies] in a thread from it, oldest first.
+  Future<({String rootId, IList<String> replyIds})> sendThread(
+    String roomId,
+    String rootBody,
+    IList<String> replies,
+  ) async {
+    final rootId = await send(roomId, rootBody);
+    // One at a time, so they're in order (oops earlier tests weren't reproducable)
+    final replyIds = await Stream.fromIterable(replies)
+        .asyncMap((body) => send(roomId, body, threadRoot: rootId))
+        .toList();
+    return (rootId: rootId, replyIds: replyIds.toIList());
+  }
+
+  /// Edits the text message [eventId] to say [body].
+  Future<String> edit(String roomId, String eventId, String body) =>
+      sendEvent(roomId, "m.room.message", {
+        "msgtype": "m.text",
+        "body": "* $body",
+        "m.new_content": {"msgtype": "m.text", "body": body},
+        "m.relates_to": {"rel_type": "m.replace", "event_id": eventId},
+      });
+
+  Future<void> redact(String roomId, String eventId) => request(
+    "PUT",
+    "/_matrix/client/v3/rooms/${Uri.encodeComponent(roomId)}/redact/"
+        "${Uri.encodeComponent(eventId)}/${DateTime.now().microsecondsSinceEpoch}",
+    accessToken: accessToken,
+  );
+
+  /// The bodies of the replies in the thread from [threadRoot], oldest first.
+  Future<IList<String>> threadReplies(String roomId, String threadRoot) async {
+    final json = await request(
+      "GET",
+      "/_matrix/client/v1/rooms/${Uri.encodeComponent(roomId)}/relations/"
+          "${Uri.encodeComponent(threadRoot)}/m.thread?dir=f&limit=100",
+      accessToken: accessToken,
+    );
+    return (json["chunk"] as List)
+        .map((event) => event["content"]["body"] as String)
+        .toIList();
+  }
+
+  Future<IList<String>> threadRepliesIncluding(
+    String roomId,
+    String threadRoot,
+    String body, {
+    int attempts = 20,
+  }) async {
+    final replies = await threadReplies(roomId, threadRoot);
+    if (replies.contains(body) || attempts <= 1) return replies;
+
+    await Future.delayed(const .new(milliseconds: 500));
+    return threadRepliesIncluding(
+      roomId,
+      threadRoot,
+      body,
+      attempts: attempts - 1,
+    );
+  }
+}

integration_test/helpers/oauth.dart

@@ -0,0 +1,68 @@
+import "package:http/http.dart" as http;
+
+import "fakes.dart";
+
+/// Fake platforms that do the browser's part of OAuth on Continuwuity, logging
+/// in as [username], then hand the redirect back to Nexus.
+class OAuthFakes(final String username, final String password) {
+  final links = FakeAppLinks();
+  late final launcher = FakeUrlLauncher(onLaunch);
+
+  Future<void> onLaunch(Uri url) async {
+    if (!url.queryParameters.containsKey("code_challenge")) return;
+
+    final redirect = await authorize(url);
+    // Nexus listens for the redirect after the launch returns
+    await Future.delayed(const .new(milliseconds: 500));
+    links.open(redirect);
+  }
+
+  /// Logs in on [authorizationUrl], then confirms the grant, returning the URI
+  /// Continuwuity redirects back to the app with.
+  Future<Uri> authorize(Uri authorizationUrl) async {
+    final client = http.Client();
+    String? cookie;
+
+    Future<Uri> followRedirect(
+      String method,
+      Uri url, [
+      Map<String, String>? form,
+    ]) async {
+      final request = http.Request(method, url)
+        ..followRedirects = false
+        ..headers.addAll({
+          // Continuwuity only accepts its forms from top-level navigations
+          "Sec-Fetch-Site": "same-origin",
+          "Sec-Fetch-Mode": "navigate",
+          "Sec-Fetch-Dest": "document",
+          "Cookie": ?cookie,
+        });
+      if (form != null) request.bodyFields = form;
+
+      final response = await http.Response.fromStream(
+        await client.send(request),
+      );
+      if (response.headers["set-cookie"] case final setCookie?) {
+        cookie = setCookie.split(";").first;
+      }
+
+      return switch ((response.statusCode, response.headers["location"])) {
+        (302 || 303 || 307, final location?) => url.resolve(location),
+        (final status, _) => throw StateError(
+          "Expected $method $url to redirect, got $status: ${response.body}",
+        ),
+      };
+    }
+
+    try {
+      final loginUrl = await followRedirect("GET", authorizationUrl);
+      final grantUrl = await followRedirect("POST", loginUrl, {
+        "identifier": username,
+        "password": password,
+      });
+      return await followRedirect("POST", grantUrl, {"stage": "confirm"});
+    } finally {
+      client.close();
+    }
+  }
+}

integration_test/helpers/pump_until.dart

@@ -0,0 +1,56 @@
+import "package:fast_immutable_collections/fast_immutable_collections.dart";
+import "package:flutter_test/flutter_test.dart";
+import "package:material_ui/material_ui.dart";
+import "package:nexus/widgets/error_dialog.dart";
+
+// Custom because `patrol_finder` gives me jQuery vibes, and that's Not GoodTM
+extension PumpUntil on WidgetTester {
+  /// Pumps until [finder] finds something, failing if it doesn't within 30
+  /// seconds, or if the app shows an error.
+  Future<void> pumpUntil(Finder finder) async {
+    const timeout = Duration(seconds: 30);
+
+    String textsIn(Finder finder) => widgetList<Text>(
+      find.descendant(of: finder, matching: find.byType(Text)),
+    ).map((text) => text.data).nonNulls.join("\n");
+
+    final stopwatch = Stopwatch()..start();
+    while (stopwatch.elapsed < timeout) {
+      await pump(const .new(milliseconds: 100));
+
+      if (finder.evaluate().isNotEmpty) return;
+
+      final errorDialog = find.byType(ErrorDialog);
+      if (errorDialog.evaluate().isNotEmpty) {
+        fail(
+          "The app showed an error while waiting for $finder:\n"
+          "${textsIn(errorDialog)}",
+        );
+      }
+    }
+
+    final snackBar = find.byType(SnackBar);
+    final shown = find
+        .byType(RichText)
+        .hitTestable()
+        .evaluate()
+        .map((element) => (element.widget as RichText).text.toPlainText())
+        .where((text) => text.trim().isNotEmpty)
+        .toIList()
+        .removeDuplicates()
+        .join(" | ");
+    fail(
+      "Timed out after $timeout waiting for $finder"
+      "${snackBar.evaluate().isEmpty ? "" : "\nSnack bar: ${textsIn(snackBar)}"}"
+      "\nShown: $shown",
+    );
+  }
+
+  /// Taps [finder] once it can be tapped, like after animating in.
+  Future<void> tapWhenShown(Finder finder) async {
+    final tappable = finder.hitTestable();
+    await pumpUntil(tappable);
+    await tap(tappable.first);
+    await pump();
+  }
+}

integration_test/helpers/test_app.dart

@@ -0,0 +1,115 @@
+import "package:app_links_platform_interface/app_links_platform_interface.dart";
+import "package:flutter_test/flutter_test.dart";
+import "package:material_ui/material_ui.dart";
+import "package:media_kit/media_kit.dart";
+import "package:nexus/controllers/active_account.dart";
+import "package:nexus/main.dart" as nexus;
+import "package:nexus/widgets/account_scope.dart";
+import "package:nexus/widgets/pages/chat.dart";
+import "package:nexus/widgets/pages/select_server.dart";
+import "package:nexus/widgets/pages/verify.dart";
+import "package:nexus/widgets/room_chat/room_chat.dart";
+import "package:url_launcher_platform_interface/url_launcher_platform_interface.dart";
+
+import "matrix_user.dart";
+import "oauth.dart";
+import "pump_until.dart";
+
+/// Nexus, run as the account [username], which is set up through the UI the
+/// first time it's opened.
+class TestApp(final String username, final String password) {
+  late final fakes = OAuthFakes(username, password);
+
+  void setUp() {
+    nexus.isInBackground = false;
+    MediaKit.ensureInitialized();
+    AppLinksPlatform.instance = fakes.links;
+    UrlLauncherPlatform.instance = fakes.launcher;
+
+    // A tap that misses would otherwise only warn
+    WidgetController.hitTestWarningShouldBeFatal = true;
+  }
+
+  Future<void> join(MatrixUser inviter, String roomId) async {
+    final user = await MatrixUser.login(username, password);
+    await inviter.invite(roomId, user.userId);
+    await user.join(roomId);
+    await user.logout();
+  }
+
+  /// Starts Nexus like [open], then opens [roomName].
+  Future<void> openRoom(WidgetTester tester, String roomName) async {
+    await open(tester);
+    await selectRoom(tester, roomName);
+  }
+
+  /// Taps [roomName] in the room list, opening the drawer it's in first when
+  /// the window is narrow enough for the mobile layout.
+  Future<void> selectRoom(WidgetTester tester, String roomName) async {
+    // Shown once the first sync is done, as is the drawer button on mobile
+    await tester.pumpUntil(find.byType(RoomChat));
+
+    final drawerButton = find
+        .byTooltip(const DefaultMaterialLocalizations().openAppDrawerTooltip)
+        .hitTestable();
+    if (drawerButton.evaluate().isNotEmpty) await tester.tap(drawerButton);
+    await tester.tapWhenShown(find.text(roomName));
+  }
+
+  /// Starts Nexus, logged in and verified, logging in and setting up
+  /// encryption through the UI first if it isn't.
+  Future<void> open(WidgetTester tester) async {
+    await tester.pumpWidget(
+      AccountScope(
+        initialAccountId: await ActiveAccountController.stored(),
+        retry: (_, _) => null,
+        child: nexus.App(),
+      ),
+    );
+
+    await tester.pumpUntil(
+      find.byWidgetPredicate(
+        (widget) =>
+            widget is SelectServerPage ||
+            widget is VerifyPage ||
+            widget is ChatPage,
+      ),
+    );
+    if (find.byType(SelectServerPage).evaluate().isNotEmpty) {
+      await logIn(tester);
+    }
+    if (find.byType(VerifyPage).evaluate().isNotEmpty) {
+      await setUpEncryption(tester);
+    }
+    await tester.pumpUntil(find.byType(ChatPage));
+  }
+
+  Future<void> logIn(WidgetTester tester) async {
+    final homeserverField = find.widgetWithText(TextField, "Homeserver URL");
+    await tester.pumpUntil(homeserverField);
+    await tester.enterText(homeserverField, homeserver);
+    await tester.testTextInput.receiveAction(.done);
+
+    // Discovery only uses HTTPS, which the test homeserver doesn't serve, so
+    // Nexus offers to log in with the URL as typed
+    await tester.tapWhenShown(find.text("Attempt log in anyways"));
+
+    // Nexus opens the authorization page, which fakes authorizes
+    await tester.pumpUntil(
+      find.byWidgetPredicate(
+        (widget) => widget is VerifyPage || widget is ChatPage,
+      ),
+    );
+  }
+
+  /// Sets up encryption from the verify page, for an account without it.
+  Future<void> setUpEncryption(WidgetTester tester) async {
+    await tester.pumpUntil(find.text("Set Up Encryption"));
+    await tester.tapWhenShown(find.widgetWithText(TextButton, "Set Up"));
+
+    await tester.tapWhenShown(find.text("I've saved my recovery key"));
+    await tester.tapWhenShown(find.widgetWithText(TextButton, "Set Up"));
+
+    await tester.tapWhenShown(find.widgetWithText(TextButton, "Done"));
+  }
+}

integration_test/helpers/threads.dart

@@ -0,0 +1,34 @@
+import "package:flutter_test/flutter_test.dart";
+import "package:material_ui/material_ui.dart";
+
+import "pump_until.dart";
+
+extension MessageFinders on CommonFinders {
+  Finder message(String body) => textContaining(body, findRichText: true);
+}
+
+extension RelativeFinders on Finder {
+  Finder inside(Type type) =>
+      find.descendant(of: find.byType(type), matching: this);
+
+  /// The [InkWell] ancestor around what this finds
+  Finder get inkWell => find.ancestor(of: this, matching: find.byType(InkWell));
+}
+
+extension ReplyCounts on WidgetTester {
+  /// Waits for a reply count in widgets of [type], then checks it, so a wrong
+  /// count fails straight away with what was shown.
+  Future<void> expectReplyCount(Type type, int expected) async {
+    final repliesLabel = RegExp(r"^(\d+) repl(?:y|ies)$");
+    final labels = find.textContaining(repliesLabel).inside(type);
+    await pumpUntil(labels);
+
+    final shown = widgetList<Text>(labels)
+        .map((label) => label.data)
+        .nonNulls
+        .map(repliesLabel.firstMatch)
+        .nonNulls
+        .map((match) => int.parse(match[1]!));
+    expect(shown, everyElement(expected), reason: "Reply count in $type");
+  }
+}

integration_test/long_thread_test.dart

@@ -0,0 +1,115 @@
+import "package:fast_immutable_collections/fast_immutable_collections.dart";
+import "package:flutter_test/flutter_test.dart";
+import "package:integration_test/integration_test.dart";
+import "package:material_ui/material_ui.dart";
+import "package:nexus/widgets/room_chat/room_chat.dart";
+import "package:nexus/widgets/thread_drawer.dart";
+import "package:nexus/widgets/threads_drawer.dart";
+
+import "helpers/matrix_user.dart";
+import "helpers/test_app.dart";
+import "helpers/pump_until.dart";
+import "helpers/threads.dart";
+
+/// A thread longer than gomuks' initial sync, which gets the latest 100
+/// events, so its start only reaches Nexus through `/relations`. That needs
+/// an account whose first sync is after the thread exists, so it's not the one
+/// other tests use.
+void main() {
+  IntegrationTestWidgetsFlutterBinding.ensureInitialized();
+
+  final app = TestApp("carol", "carolpass");
+  setUpAll(app.setUp);
+  final run = DateTime.now().millisecondsSinceEpoch;
+  final roomName = "Long thread $run";
+  final rootBody = "Long thread root $run";
+  const replyCount = 120;
+  // Among the first replies, which aren't synced
+  const jumpedTo = 10;
+  // Padded, so no reply's text contains another's (oops those failures were confusing when I didn't do that)
+  String reply(int number) => "Long reply ${number.toString().padLeft(3, "0")}";
+
+  setUpAll(() async {
+    final bob = await MatrixUser.login("bob", "bobpass");
+    final roomId = await bob.createRoom(roomName);
+    await app.join(bob, roomId);
+
+    final thread = await bob.sendThread(
+      roomId,
+      rootBody,
+      Iterable.generate(replyCount, (index) => reply(index + 1)).toIList(),
+    );
+    // In the room's timeline, so there's something to jump from, to a reply
+    // with others on both sides that aren't synced either
+    await bob.send(
+      roomId,
+      "Quoting an old reply",
+      replyTo: thread.replyIds[jumpedTo - 1],
+    );
+  });
+
+  /// Drags the open thread by [offset] until [finder] is shown in it, loading
+  /// more replies as it goes, for up to 30 seconds.
+  Future<void> scrollThread(
+    WidgetTester tester,
+    Finder finder,
+    Offset offset,
+  ) => tester.dragUntilVisible(
+    finder.inside(ThreadDrawer),
+    find.byType(CustomScrollView).inside(ThreadDrawer).first,
+    offset,
+    maxIteration: 60,
+    duration: const .new(milliseconds: 500),
+  );
+
+  Future<void> openThreadsDrawer(WidgetTester tester) async {
+    await app.openRoom(tester, roomName);
+    await tester.tapWhenShown(find.byTooltip("Open threads"));
+    await tester.pumpUntil(find.message(rootBody).inside(ThreadsDrawer));
+  }
+
+  testWidgets("lists the thread with all of its replies", (tester) async {
+    await openThreadsDrawer(tester);
+
+    await tester.expectReplyCount(ThreadsDrawer, replyCount);
+  });
+
+  // Before the whole thread is loaded by scrolling through it below
+  testWidgets("jumps to a reply in the thread that isn't loaded", (
+    tester,
+  ) async {
+    await app.openRoom(tester, roomName);
+
+    // The quote of the reply is fetched on its own, then tapped
+    await tester.tapWhenShown(
+      find.message(reply(jumpedTo)).inside(RoomChat).inkWell,
+    );
+
+    // The thread opens around the reply, with replies on both sides
+    await tester.pumpUntil(
+      find.message(reply(jumpedTo)).inside(ThreadDrawer).hitTestable(),
+    );
+    await tester.pumpUntil(
+      find.message(reply(jumpedTo - 1)).inside(ThreadDrawer),
+    );
+    await tester.pumpUntil(
+      find.message(reply(jumpedTo + 1)).inside(ThreadDrawer),
+    );
+
+    await scrollThread(tester, find.message(reply(60)), const .new(0, -400));
+  });
+
+  testWidgets("loads older replies back to the root", (tester) async {
+    await openThreadsDrawer(tester);
+    await tester.tapWhenShown(
+      find.message(rootBody).inside(ThreadsDrawer).inkWell,
+    );
+    await tester.pumpUntil(
+      find.message(reply(replyCount)).inside(ThreadDrawer),
+    );
+
+    // Dragging down scrolls up the reversed timeline, to older replies
+    await scrollThread(tester, find.message(rootBody), const .new(0, 400));
+    expect(find.message(reply(1)).inside(ThreadDrawer), findsWidgets);
+  });
+}

integration_test/threads_test.dart

@@ -0,0 +1,258 @@
+import "package:flutter_test/flutter_test.dart";
+import "package:integration_test/integration_test.dart";
+import "package:material_ui/material_ui.dart";
+import "package:nexus/widgets/composer/composer.dart";
+import "package:nexus/widgets/room_chat/room_chat.dart";
+import "package:nexus/widgets/thread_drawer.dart";
+import "package:nexus/widgets/thread_summary.dart";
+import "package:nexus/widgets/threads_drawer.dart";
+
+import "helpers/matrix_user.dart";
+import "helpers/test_app.dart";
+import "helpers/pump_until.dart";
+import "helpers/threads.dart";
+
+void main() {
+  IntegrationTestWidgetsFlutterBinding.ensureInitialized();
+
+  final app = TestApp("alice", "alicepass");
+  setUpAll(app.setUp);
+  final run = DateTime.now().millisecondsSinceEpoch;
+  late MatrixUser bob;
+
+  setUpAll(() async => bob = await MatrixUser.login("bob", "bobpass"));
+
+  /// Opens [roomName], waiting for the thread from [rootBody] in its timeline.
+  Future<void> openRoom(
+    WidgetTester tester,
+    String roomName,
+    String rootBody,
+  ) async {
+    await app.openRoom(tester, roomName);
+    await tester.pumpUntil(
+      find.message(rootBody).inside(RoomChat).hitTestable(),
+    );
+  }
+
+  /// Opens the thread from the room's summary, waiting for [reply] in it.
+  Future<void> openThread(WidgetTester tester, String reply) async {
+    await tester.tapWhenShown(find.byType(ThreadSummary));
+    await tester.pumpUntil(find.message(reply).inside(ThreadDrawer));
+  }
+
+  group("a thread", () {
+    final roomName = "Threads $run";
+    final rootBody = "Thread root $run";
+    const firstReply = "First reply";
+    const secondReply = "Second reply";
+
+    late String roomId;
+    late String rootId;
+
+    setUpAll(() async {
+      roomId = await bob.createRoom(roomName);
+      // Joined before Nexus logs in, so the room is there once it does
+      await app.join(bob, roomId);
+
+      rootId = (await bob.sendThread(
+        roomId,
+        rootBody,
+        .new([firstReply, secondReply]),
+      )).rootId;
+    });
+
+    Future<int> replyCount() async =>
+        (await bob.threadReplies(roomId, rootId)).length;
+
+    testWidgets("logs in with OAuth and sets up encryption", (tester) async {
+      await app.open(tester);
+
+      await app.selectRoom(tester, roomName);
+    });
+
+    testWidgets("summarises the thread under its root", (tester) async {
+      await openRoom(tester, roomName, rootBody);
+
+      await tester.expectReplyCount(ThreadSummary, 2);
+      expect(find.message(secondReply).inside(ThreadSummary), findsWidgets);
+      // Replies are in the thread, not the room's timeline
+      expect(find.message(firstReply), findsNothing);
+    });
+
+    testWidgets("lists the thread in the threads drawer", (tester) async {
+      await openRoom(tester, roomName, rootBody);
+      await tester.tapWhenShown(find.byTooltip("Open threads"));
+
+      await tester.pumpUntil(find.message(rootBody).inside(ThreadsDrawer));
+      await tester.expectReplyCount(ThreadsDrawer, 2);
+      expect(find.text("Last active:").inside(ThreadsDrawer), findsOneWidget);
+    });
+
+    testWidgets("opens the thread from the threads drawer", (tester) async {
+      await openRoom(tester, roomName, rootBody);
+      await tester.tapWhenShown(find.byTooltip("Open threads"));
+      await tester.tapWhenShown(
+        find.message(rootBody).inside(ThreadsDrawer).inkWell,
+      );
+
+      await tester.pumpUntil(find.message(secondReply).inside(ThreadDrawer));
+    });
+
+    testWidgets("shows the root and its replies, oldest first", (tester) async {
+      await openRoom(tester, roomName, rootBody);
+      await openThread(tester, secondReply);
+
+      final root = find.message(rootBody).inside(ThreadDrawer).first;
+      final first = find.message(firstReply).inside(ThreadDrawer).first;
+      final second = find.message(secondReply).inside(ThreadDrawer).first;
+      expect(root, findsOneWidget);
+      expect(first, findsOneWidget);
+      expect(
+        tester.getTopLeft(root).dy,
+        lessThan(tester.getTopLeft(first).dy),
+        reason: "The root should be above the replies",
+      );
+      expect(
+        tester.getTopLeft(first).dy,
+        lessThan(tester.getTopLeft(second).dy),
+        reason: "Older replies should be above newer ones",
+      );
+    });
+
+    testWidgets("sends replies to the thread", (tester) async {
+      final body = "Reply from Nexus $run";
+      final before = await replyCount();
+      await openRoom(tester, roomName, rootBody);
+      await openThread(tester, secondReply);
+
+      final composer = find
+          .widgetWithText(TextField, "Your message here...")
+          .inside(ThreadDrawer);
+      await tester.pumpUntil(composer);
+      await tester.enterText(composer, body);
+      await tester.tapWhenShown(
+        find.byTooltip("Send message").inside(ThreadDrawer),
+      );
+      await tester.pumpUntil(find.message(body).inside(ThreadDrawer));
+
+      // It's in the thread for other clients too
+      final replies = await bob.threadRepliesIncluding(roomId, rootId, body);
+      expect(replies.last, body);
+
+      // Shown as the latest reply once the summary has caught up
+      await tester.pumpUntil(find.message(body).inside(ThreadSummary));
+      await tester.expectReplyCount(ThreadSummary, before + 1);
+      expect(
+        find.text(body).inside(Composer),
+        findsNothing,
+        reason: "The composer should be cleared once sent",
+      );
+    });
+
+    testWidgets("shows replies from others as they arrive", (tester) async {
+      final body = "Live reply $run";
+      await openRoom(tester, roomName, rootBody);
+      await openThread(tester, secondReply);
+
+      final before = await replyCount();
+      await bob.send(roomId, body, threadRoot: rootId);
+
+      await tester.pumpUntil(find.message(body).inside(ThreadDrawer));
+      await tester.pumpUntil(find.message(body).inside(ThreadSummary));
+      await tester.expectReplyCount(ThreadSummary, before + 1);
+    });
+  });
+
+  group("redactions", () {
+    final roomName = "Redactions $run";
+    final rootBody = "Redaction root $run";
+    const keptReply = "Kept reply";
+    const redactedReply = "Redacted reply";
+
+    late String roomId;
+    late String rootId;
+    late String redactedId;
+
+    setUpAll(() async {
+      roomId = await bob.createRoom(roomName);
+      await app.join(bob, roomId);
+
+      final thread = await bob.sendThread(
+        roomId,
+        rootBody,
+        .new([keptReply, redactedReply]),
+      );
+      rootId = thread.rootId;
+      redactedId = thread.replyIds.last;
+    });
+
+    testWidgets("drops a redacted reply from its thread", (tester) async {
+      await openRoom(tester, roomName, rootBody);
+      await tester.expectReplyCount(ThreadSummary, 2);
+
+      await bob.redact(roomId, redactedId);
+
+      // The reply before it becomes the latest
+      await tester.pumpUntil(find.message(keptReply).inside(ThreadSummary));
+      await tester.expectReplyCount(ThreadSummary, 1);
+
+      await openThread(tester, keptReply);
+      expect(find.message(redactedReply).inside(ThreadDrawer), findsNothing);
+    });
+
+    testWidgets("still opens the thread of a redacted root", (tester) async {
+      await bob.redact(roomId, rootId);
+      await app.openRoom(tester, roomName);
+      await tester.tapWhenShown(find.byTooltip("Open threads"));
+
+      // The root's preview is redacted, so the card is found by its count
+      await tester.tapWhenShown(
+        find.text("1 reply").inside(ThreadsDrawer).inkWell,
+      );
+
+      final root = find.text("Redacted event").inside(ThreadDrawer);
+      final reply = find.message(keptReply).inside(ThreadDrawer);
+      await tester.pumpUntil(root);
+      await tester.pumpUntil(reply);
+      expect(
+        tester.getTopLeft(root.first).dy,
+        lessThan(tester.getTopLeft(reply.first).dy),
+        reason: "The redacted root should still be above the replies",
+      );
+    });
+  });
+
+  group("edits", () {
+    final roomName = "Edits $run";
+    final rootBody = "Edit root $run";
+    const originalReply = "Reply before editing";
+    const editedReply = "Reply after editing";
+
+    late String roomId;
+    late String replyId;
+
+    setUpAll(() async {
+      roomId = await bob.createRoom(roomName);
+      await app.join(bob, roomId);
+
+      final thread = await bob.sendThread(
+        roomId,
+        rootBody,
+        .new([originalReply]),
+      );
+      replyId = thread.replyIds.single;
+    });
+
+    testWidgets("shows an edited reply's new text", (tester) async {
+      await openRoom(tester, roomName, rootBody);
+      await tester.pumpUntil(find.message(originalReply).inside(ThreadSummary));
+
+      await bob.edit(roomId, replyId, editedReply);
+
+      await tester.pumpUntil(find.message(editedReply).inside(ThreadSummary));
+      await openThread(tester, editedReply);
+      expect(find.message(originalReply).inside(ThreadDrawer), findsNothing);
+      expect(find.text("(edited)").inside(ThreadDrawer), findsOneWidget);
+    });
+  });
+}