test: add a block_on function to tokio-test (#1431)

tokio-test/src/lib.rs

@@ -14,6 +14,18 @@ pub mod io;
 mod macros;
 pub mod task;
 
+/// Runs the provided future, blocking the current thread until the
+/// future completes.
+///
+/// For more information, see the documentation for
+/// [`tokio::runtime::current_thread::Runtime::block_on`][runtime-block-on].
+///
+/// [runtime-block-on]: https://docs.rs/tokio/0.2.0-alpha.1/tokio/runtime/current_thread/struct.Runtime.html#method.block_on
+pub fn block_on<F: std::future::Future>(future: F) -> F::Output {
+    let mut rt = tokio::runtime::current_thread::Runtime::new().unwrap();
+    rt.block_on(future)
+}
+
 /*
 #[doc(hidden)]
 pub mod codegen {