Add tests for select_biased

Author: Xaeroxe

futures/tests/future_select_biased.rs

@@ -0,0 +1,19 @@
+use std::future::{pending, ready};
+
+use futures::future::select_biased;
+use futures_executor::block_on;
+
+#[test]
+fn is_biased() {
+    let mut results = Vec::with_capacity(100);
+    for _ in 0..100 {
+        let (i, _) = block_on(select_biased(ready(0), ready(1))).factor_first();
+        results.push(i);
+    }
+    assert!(results.iter().all(|i| *i == 0));
+}
+
+#[test]
+fn second_argument_works() {
+    assert_eq!(block_on(select_biased(pending(), ready(1))).factor_first().0, 1);
+}