Refactor async (#71)

unittests/Async/Sleep.cpp

@@ -0,0 +1,24 @@
+#include "Test/Test.h"
+#include "Async/Async.h"
+
+namespace clice::testing {
+
+namespace {
+
+TEST(Async, Sleep) {
+    int x = 1;
+    auto task_gen = [&]() -> async::Task<> {
+        x = 2;
+        co_await async::sleep(100);
+        x = 3;
+    };
+
+    auto task = task_gen();
+    async::run(task);
+
+    EXPECT_EQ(x, 3);
+}
+
+}  // namespace
+
+}  // namespace clice::testing