[Windows] Improve FlutterWindow unit tests (#50676)

_This was split from #50673 to reduce noise in that PR._

Previously `MockFlutterWindow` called a `FlutterWindow` constructor which created a window & resized it. This change introduces a minimal base constructor for testing purposes. This allows us to skip some noisy mocks in a subsequent change: #50673

This also introduces a fixture for the window unit tests.

Part of flutter/flutter#137267
Part of flutter/flutter#142845

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

Author: loic-sharma

shell/platform/windows/flutter_window.cc

@@ -121,8 +121,7 @@ FlutterWindow::FlutterWindow(
     int height,
     std::shared_ptr<WindowsProcTable> windows_proc_table,
     std::unique_ptr<TextInputManager> text_input_manager)
-    : binding_handler_delegate_(nullptr),
-      touch_id_generator_(kMinTouchDeviceId, kMaxTouchDeviceId),
+    : touch_id_generator_(kMinTouchDeviceId, kMaxTouchDeviceId),
       windows_proc_table_(std::move(windows_proc_table)),
       text_input_manager_(std::move(text_input_manager)),
       ax_fragment_root_(nullptr) {
@@ -148,13 +147,19 @@ FlutterWindow::FlutterWindow(
   current_cursor_ = ::LoadCursor(nullptr, IDC_ARROW);
 }
 
+// Base constructor for mocks
+FlutterWindow::FlutterWindow()
+    : touch_id_generator_(kMinTouchDeviceId, kMaxTouchDeviceId) {}
+
 FlutterWindow::~FlutterWindow() {
   Destroy();
 }
 
 void FlutterWindow::SetView(WindowBindingHandlerDelegate* window) {
   binding_handler_delegate_ = window;
-  direct_manipulation_owner_->SetBindingHandlerDelegate(window);
+  if (direct_manipulation_owner_) {
+    direct_manipulation_owner_->SetBindingHandlerDelegate(window);
+  }
   if (restored_ && window) {
     OnWindowStateEvent(WindowStateEvent::kShow);
   }

shell/platform/windows/flutter_window.h

@@ -194,6 +194,9 @@ class FlutterWindow : public KeyboardManager::WindowDelegate,
   virtual void OnWindowStateEvent(WindowStateEvent event);
 
  protected:
+  // Base constructor for mocks.
+  FlutterWindow();
+
   // Win32's DefWindowProc.
   //
   // Used as the fallback behavior of HandleMessage. Exposed for dependency
@@ -321,7 +324,7 @@ class FlutterWindow : public KeyboardManager::WindowDelegate,
 
   // A pointer to a FlutterWindowsView that can be used to update engine
   // windowing and input state.
-  WindowBindingHandlerDelegate* binding_handler_delegate_;
+  WindowBindingHandlerDelegate* binding_handler_delegate_ = nullptr;
 
   // The last cursor set by Flutter. Defaults to the arrow cursor.
   HCURSOR current_cursor_;

shell/platform/windows/flutter_window_unittests.cc

@@ -6,6 +6,7 @@
 #include "flutter/shell/platform/windows/flutter_window.h"
 #include "flutter/shell/platform/windows/testing/mock_window_binding_handler.h"
 #include "flutter/shell/platform/windows/testing/mock_window_binding_handler_delegate.h"
+#include "flutter/shell/platform/windows/testing/windows_test.h"
 #include "flutter/shell/platform/windows/testing/wm_builders.h"
 
 #include "gmock/gmock.h"
@@ -25,7 +26,7 @@ static constexpr int32_t kDefaultPointerDeviceId = 0;
 class MockFlutterWindow : public FlutterWindow {
  public:
   MockFlutterWindow(bool reset_view_on_exit = true)
-      : FlutterWindow(800, 600), reset_view_on_exit_(reset_view_on_exit) {
+      : FlutterWindow(), reset_view_on_exit_(reset_view_on_exit) {
     ON_CALL(*this, GetDpiScale())
         .WillByDefault(Return(this->FlutterWindow::GetDpiScale()));
   }
@@ -107,14 +108,16 @@ class MockFlutterWindowsView : public FlutterWindowsView {
   FML_DISALLOW_COPY_AND_ASSIGN(MockFlutterWindowsView);
 };
 
+class FlutterWindowTest : public WindowsTest {};
+
 }  // namespace
 
-TEST(FlutterWindowTest, CreateDestroy) {
+TEST_F(FlutterWindowTest, CreateDestroy) {
   FlutterWindow window(800, 600);
   ASSERT_TRUE(TRUE);
 }
 
-TEST(FlutterWindowTest, OnBitmapSurfaceUpdated) {
+TEST_F(FlutterWindowTest, OnBitmapSurfaceUpdated) {
   FlutterWindow win32window(100, 100);
   int old_handle_count = GetGuiResources(GetCurrentProcess(), GR_GDIOBJECTS);
 
@@ -131,7 +134,7 @@ TEST(FlutterWindowTest, OnBitmapSurfaceUpdated) {
 // Tests that composing rect updates are transformed from Flutter logical
 // coordinates to device coordinates and passed to the text input manager
 // when the DPI scale is 100% (96 DPI).
-TEST(FlutterWindowTest, OnCursorRectUpdatedRegularDPI) {
+TEST_F(FlutterWindowTest, OnCursorRectUpdatedRegularDPI) {
   MockFlutterWindow win32window;
   EXPECT_CALL(win32window, GetDpiScale()).WillOnce(Return(1.0));
 
@@ -144,7 +147,7 @@ TEST(FlutterWindowTest, OnCursorRectUpdatedRegularDPI) {
 // Tests that composing rect updates are transformed from Flutter logical
 // coordinates to device coordinates and passed to the text input manager
 // when the DPI scale is 150% (144 DPI).
-TEST(FlutterWindowTest, OnCursorRectUpdatedHighDPI) {
+TEST_F(FlutterWindowTest, OnCursorRectUpdatedHighDPI) {
   MockFlutterWindow win32window;
   EXPECT_CALL(win32window, GetDpiScale()).WillOnce(Return(1.5));
 
@@ -155,7 +158,7 @@ TEST(FlutterWindowTest, OnCursorRectUpdatedHighDPI) {
   win32window.OnCursorRectUpdated(cursor_rect);
 }
 
-TEST(FlutterWindowTest, OnPointerStarSendsDeviceType) {
+TEST_F(FlutterWindowTest, OnPointerStarSendsDeviceType) {
   FlutterWindow win32window(100, 100);
   MockWindowBindingHandlerDelegate delegate;
   EXPECT_CALL(delegate, OnWindowStateEvent).Times(AnyNumber());
@@ -256,15 +259,16 @@ TEST(FlutterWindowTest, OnPointerStarSendsDeviceType) {
 
 // Tests that calls to OnScroll in turn calls GetScrollOffsetMultiplier
 // for mapping scroll ticks to pixels.
-TEST(FlutterWindowTest, OnScrollCallsGetScrollOffsetMultiplier) {
+TEST_F(FlutterWindowTest, OnScrollCallsGetScrollOffsetMultiplier) {
   MockFlutterWindow win32window;
   MockWindowBindingHandlerDelegate delegate;
   EXPECT_CALL(win32window, OnWindowStateEvent).Times(AnyNumber());
   win32window.SetView(&delegate);
 
-  ON_CALL(win32window, GetScrollOffsetMultiplier())
-      .WillByDefault(Return(120.0f));
-  EXPECT_CALL(win32window, GetScrollOffsetMultiplier()).Times(1);
+  EXPECT_CALL(win32window, GetWindowHandle).WillOnce([&win32window]() {
+    return win32window.FlutterWindow::GetWindowHandle();
+  });
+  EXPECT_CALL(win32window, GetScrollOffsetMultiplier).WillOnce(Return(120.0f));
 
   EXPECT_CALL(delegate,
               OnScroll(_, _, 0, 0, 120.0f, kFlutterPointerDeviceKindMouse,
@@ -275,7 +279,7 @@ TEST(FlutterWindowTest, OnScrollCallsGetScrollOffsetMultiplier) {
                        kDefaultPointerDeviceId);
 }
 
-TEST(FlutterWindowTest, OnWindowRepaint) {
+TEST_F(FlutterWindowTest, OnWindowRepaint) {
   MockFlutterWindow win32window;
   MockWindowBindingHandlerDelegate delegate;
   EXPECT_CALL(win32window, OnWindowStateEvent).Times(AnyNumber());
@@ -286,7 +290,7 @@ TEST(FlutterWindowTest, OnWindowRepaint) {
   win32window.InjectWindowMessage(WM_PAINT, 0, 0);
 }
 
-TEST(FlutterWindowTest, OnThemeChange) {
+TEST_F(FlutterWindowTest, OnThemeChange) {
   MockFlutterWindow win32window;
   MockWindowBindingHandlerDelegate delegate;
   EXPECT_CALL(win32window, OnWindowStateEvent).Times(AnyNumber());
@@ -300,15 +304,15 @@ TEST(FlutterWindowTest, OnThemeChange) {
 // The window should return no root accessibility node if
 // it isn't attached to a view.
 // Regression test for https://github.com/flutter/flutter/issues/129791
-TEST(FlutterWindowTest, AccessibilityNodeWithoutView) {
+TEST_F(FlutterWindowTest, AccessibilityNodeWithoutView) {
   MockFlutterWindow win32window;
 
   EXPECT_EQ(win32window.GetNativeViewAccessible(), nullptr);
 }
 
 // Ensure that announcing the alert propagates the message to the alert node.
 // Different screen readers use different properties for alerts.
-TEST(FlutterWindowTest, AlertNode) {
+TEST_F(FlutterWindowTest, AlertNode) {
   std::unique_ptr<MockFlutterWindow> win32window =
       std::make_unique<MockFlutterWindow>();
   EXPECT_CALL(*win32window.get(), GetAxFragmentRootDelegate())
@@ -338,7 +342,7 @@ TEST(FlutterWindowTest, AlertNode) {
   EXPECT_EQ(role.lVal, ROLE_SYSTEM_ALERT);
 }
 
-TEST(FlutterWindowTest, LifecycleFocusMessages) {
+TEST_F(FlutterWindowTest, LifecycleFocusMessages) {
   MockFlutterWindow win32window;
   EXPECT_CALL(win32window, GetWindowHandle)
       .WillRepeatedly(Return(reinterpret_cast<HWND>(1)));
@@ -370,7 +374,7 @@ TEST(FlutterWindowTest, LifecycleFocusMessages) {
   EXPECT_EQ(last_event, WindowStateEvent::kUnfocus);
 }
 
-TEST(FlutterWindowTest, CachedLifecycleMessage) {
+TEST_F(FlutterWindowTest, CachedLifecycleMessage) {
   MockFlutterWindow win32window;
   EXPECT_CALL(win32window, GetWindowHandle)
       .WillRepeatedly(Return(reinterpret_cast<HWND>(1)));
@@ -403,7 +407,7 @@ TEST(FlutterWindowTest, CachedLifecycleMessage) {
   EXPECT_TRUE(restored);
 }
 
-TEST(FlutterWindowTest, UpdateCursor) {
+TEST_F(FlutterWindowTest, UpdateCursor) {
   FlutterWindow win32window(100, 100);
   win32window.UpdateFlutterCursor("text");
   HCURSOR cursor = ::GetCursor();