Add basic timer test.

tests/0-timer.d

@@ -0,0 +1,55 @@
+/++ dub.sdl:
+	name "test"
+	dependency "eventcore" path=".."
++/
+module test;
+
+import eventcore.core;
+import std.datetime : Clock, SysTime, UTC;
+import std.stdio : writefln;
+import core.time : Duration, msecs;
+
+SysTime s_startTime;
+int s_cnt = 0;
+bool s_done;
+
+void main()
+{
+	s_startTime = Clock.currTime(UTC());
+
+	auto tm = eventDriver.timers.create();
+	eventDriver.timers.wait(tm, (tm) nothrow @safe {
+		scope (failure) assert(false);
+
+		auto dur = Clock.currTime(UTC()) - s_startTime;
+		assert(dur > 200.msecs);
+		assert(dur < 220.msecs);	
+
+		s_startTime = Clock.currTime(UTC());
+		eventDriver.timers.set(tm, 100.msecs, 100.msecs);
+
+		void secondTier(TimerID timer) nothrow @safe {
+			scope (failure) assert(false);
+			auto dur = Clock.currTime(UTC()) - s_startTime;
+			s_cnt++;
+			assert(dur > 100.msecs * s_cnt);
+			assert(dur < 100.msecs * s_cnt + 20.msecs);
+
+			if (s_cnt == 3) {
+				s_done = true;
+				eventDriver.core.exit();
+			} else eventDriver.timers.wait(tm, &secondTier);
+		}
+
+		eventDriver.timers.wait(tm, &secondTier);
+	});
+
+	eventDriver.timers.set(tm, 200.msecs, 0.msecs);
+
+	ExitReason er;
+	do er = eventDriver.core.processEvents(Duration.max);
+	while (er == ExitReason.idle);
+	//assert(er == ExitReason.outOfWaiters); // FIXME: see above
+	assert(s_done);
+	s_done = false;
+}