Add test case for #58.

tests/issue-58-task-already-scheduled.d

@@ -0,0 +1,46 @@
+/+ dub.sdl:
+	name "tests"
+	dependency "vibe-core" path=".."
++/
+module tests;
+
+import vibe.core.sync;
+import vibe.core.core;
+import std.datetime;
+import core.atomic;
+
+shared ManualEvent ev;
+shared size_t counter;
+
+shared static this()
+{
+	ev = createSharedManualEvent();
+}
+
+void main()
+{
+	setTaskStackSize(64*1024);
+
+	runTask({
+		foreach (x; 0 .. 500) {
+			runWorkerTask(&worker);
+		}
+	});
+
+	setTimer(dur!"msecs"(10), { ev.emit(); });
+	setTimer(dur!"seconds"(20), { assert(false, "Timers didn't fire within the time limit"); });
+
+	runApplication();
+
+	assert(atomicLoad(counter) == 500, "Event loop exited prematurely.");
+}
+
+void worker()
+{
+	ev.wait();
+	ev.emit();
+	setTimer(dur!"seconds"(1), {
+		auto c = atomicOp!"+="(counter, 1);
+		if (c == 500) exitEventLoop(true);
+	});
+}