Use Catch for our test suite

`make check` is also added to compile and run the tests
Catch is fetched with cmake automatically into the build directory when needed

tests/timed_events.cpp

@@ -0,0 +1,62 @@
+#include "catch.hpp"
+
+#include <utils/timed_events.hpp>
+
+/**
+ * Let Catch know how to display std::chrono::duration values
+ */
+namespace Catch
+{
+  template<typename Rep, typename Period> struct StringMaker<std::chrono::duration<Rep, Period>>
+  {
+    static std::string convert(const std::chrono::duration<Rep, Period>& value)
+    {
+      return  std::to_string(std::chrono::duration_cast<std::chrono::milliseconds>(value).count()) + "ms";
+    }
+  };
+}
+
+/**
+ * TODO, use a mock clock instead of relying on the real time with a sleep:
+ * it’s unreliable on heavy load.
+ */
+#include <thread>
+
+TEST_CASE("Test timed event expiration")
+{
+  SECTION("Check what happens when there is no events")
+    {
+      CHECK(TimedEventsManager::instance().get_timeout() == utils::no_timeout);
+      CHECK(TimedEventsManager::instance().execute_expired_events() == 0);
+    }
+
+  // Add a single event
+  TimedEventsManager::instance().add_event(TimedEvent(std::chrono::steady_clock::now() + 50ms, [](){}));
+
+  // The event should not yet be expired
+  CHECK(TimedEventsManager::instance().get_timeout() > 0ms);
+  CHECK(TimedEventsManager::instance().execute_expired_events() == 0);
+
+  std::chrono::milliseconds timoute = TimedEventsManager::instance().get_timeout();
+  INFO("Sleeping for " << timoute.count() << "ms");
+  std::this_thread::sleep_for(timoute);
+
+  // Event is now expired
+  CHECK(TimedEventsManager::instance().execute_expired_events() == 1);
+  CHECK(TimedEventsManager::instance().get_timeout() == utils::no_timeout);
+}
+
+TEST_CASE("Test timed event cancellation")
+{
+  auto now = std::chrono::steady_clock::now();
+  TimedEventsManager::instance().add_event(TimedEvent(now + 100ms, [](){ }, "un"));
+  TimedEventsManager::instance().add_event(TimedEvent(now + 200ms, [](){ }, "deux"));
+  TimedEventsManager::instance().add_event(TimedEvent(now + 300ms, [](){ }, "deux"));
+
+  CHECK(TimedEventsManager::instance().get_timeout() > 0ms);
+  CHECK(TimedEventsManager::instance().size() == 3);
+  CHECK(TimedEventsManager::instance().cancel("un") == 1);
+  CHECK(TimedEventsManager::instance().size() == 2);
+  CHECK(TimedEventsManager::instance().cancel("deux") == 2);
+  CHECK(TimedEventsManager::instance().get_timeout() == utils::no_timeout);
+}