Added a basic test

cmake/ftxui_test.cmake

@@ -40,6 +40,7 @@ add_executable(ftxui-tests
   src/ftxui/dom/hyperlink_test.cpp
   src/ftxui/dom/linear_gradient_test.cpp
   src/ftxui/dom/scroll_indicator_test.cpp
+  src/ftxui/dom/selection_test.cpp
   src/ftxui/dom/separator_test.cpp
   src/ftxui/dom/spinner_test.cpp
   src/ftxui/dom/table_test.cpp

src/ftxui/dom/selection_test.cpp

@@ -0,0 +1,84 @@
+// Copyright 2022 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.
+#include <gtest/gtest.h>
+#include <csignal>  // for raise, SIGABRT, SIGFPE, SIGILL, SIGINT, SIGSEGV, SIGTERM
+
+#include "ftxui/dom/elements.hpp"  // for text
+#include "ftxui/dom/node.hpp"      // for Render
+#include "ftxui/screen/screen.hpp"  // for Screen
+#include "ftxui/component/event.hpp"           // for Event
+#include "ftxui/component/mouse.hpp"  // for Mouse, Mouse::Left, Mouse::Pressed, Mouse::Released
+#include "ftxui/component/component.hpp"       // for Input, Renderer, Vertical
+#include "ftxui/component/screen_interactive.hpp"
+#include "ftxui/component/loop.hpp"       // for Loop
+
+
+// NOLINTBEGIN
+namespace ftxui {
+
+namespace {
+Event MousePressed(int x, int y) {
+  Mouse mouse;
+  mouse.button = Mouse::Left;
+  mouse.motion = Mouse::Pressed;
+  mouse.shift = false;
+  mouse.meta = false;
+  mouse.control = false;
+  mouse.x = x;
+  mouse.y = y;
+  return Event::Mouse("jjj", mouse);
+}
+
+Event MouseReleased(int x, int y) {
+  Mouse mouse;
+  mouse.button = Mouse::Left;
+  mouse.motion = Mouse::Released;
+  mouse.shift = false;
+  mouse.meta = false;
+  mouse.control = false;
+  mouse.x = x;
+  mouse.y = y;
+  return Event::Mouse("jjj", mouse);
+}
+}  // namespace
+
+
+TEST(SelectionTest, BasicSelection) {
+
+  int selectionChangeCounter = 0;
+
+  auto component = Renderer([&] {
+      return text("Lorem ipsum dolor");
+  });
+  auto screen = ScreenInteractive::FixedSize(20, 1);
+
+  screen.setSelectionOptions({
+    .transform = [](Pixel& pixel) {
+      pixel.inverted = true;
+    },
+    .on_change = [&] {
+      selectionChangeCounter++;
+    }
+  });
+
+  Loop loop(&screen, component);
+
+  loop.RunOnce();
+  screen.PostEvent(MousePressed(3, 1));
+  loop.RunOnce();
+  screen.PostEvent(MouseReleased(10, 1));
+  loop.RunOnce();
+
+  EXPECT_EQ(selectionChangeCounter, 2);
+
+  Render(screen, component->Render());
+
+  EXPECT_EQ(screen.ToString(), "\x1B[7mL\x1B[27morem ipsum dolor   ");
+
+  EXPECT_STREQ(screen.GetSelectedContent(component).c_str(), "rem ipsu");
+}
+
+
+}  // namespace ftxui
+// NOLINTEND