Add regression test for issue 31.

See https://github.com/ArthurSonzogni/FTXUI/issues/31

Due to a bug fixed by:
https://github.com/ArthurSonzogni/FTXUI/pull/32
the character 'P' was not correctly converted into event.

CMakeLists.txt

@@ -174,10 +174,11 @@ if (FTXUI_BUILD_TESTS AND ${CMAKE_VERSION} VERSION_GREATER "3.11.4")
   endif()
 
   add_executable(tests
-    src/ftxui/component/toggle_test.cpp
-    src/ftxui/component/radiobox_test.cpp
     src/ftxui/component/container_test.cpp
+    src/ftxui/component/event_test.cpp
+    src/ftxui/component/radiobox_test.cpp
     src/ftxui/component/receiver_test.cpp
+    src/ftxui/component/toggle_test.cpp
     src/ftxui/dom/gauge_test.cpp
     src/ftxui/dom/hbox_test.cpp
     src/ftxui/dom/text_test.cpp

src/ftxui/component/event_test.cpp

@@ -0,0 +1,49 @@
+// Copyright 2020 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 "ftxui/component/event.hpp"
+#include "ftxui/component/receiver.hpp"
+
+#include "gtest/gtest.h"
+
+using namespace ftxui;
+
+namespace {
+// Produce a stream of Event from a stream of char.
+void CharToEventStream(Receiver<char> receiver, Sender<Event> sender) {
+  char c;
+  while (receiver->Receive(&c))
+    Event::Convert(receiver, sender, c);
+}
+
+}  // namespace
+
+// Test char |c| to are trivially converted into |Event::Character(c)|.
+TEST(Event, Character) {
+  std::vector<char> basic_char;
+  for (char c = 'a'; c < 'z'; ++c)
+    basic_char.push_back(c);
+  for (char c = 'A'; c < 'Z'; ++c)
+    basic_char.push_back(c);
+
+  auto char_receiver = MakeReceiver<char>();
+  auto char_sender = char_receiver->MakeSender();
+
+  auto event_receiver = MakeReceiver<Event>();
+  auto event_sender = event_receiver->MakeSender();
+
+  for (char c : basic_char)
+    char_sender->Send(c);
+  char_sender.reset();
+
+  CharToEventStream(std::move(char_receiver), std::move(event_sender));
+
+  Event received;
+  for (char c : basic_char) {
+    EXPECT_TRUE(event_receiver->Receive(&received));
+    EXPECT_TRUE(received.is_character());
+    EXPECT_EQ(c, received.character());
+  }
+  EXPECT_FALSE(event_receiver->Receive(&received));
+}