1 //! Additional combinators for testing futures.
2 
3 mod pending_once;
4 pub use self::pending_once::PendingOnce;
5 
6 use futures_core::future::Future;
7 use std::thread;
8 
9 pub use crate::assert_unmoved::AssertUnmoved;
10 pub use crate::interleave_pending::InterleavePending;
11 
12 /// Additional combinators for testing futures.
13 pub trait FutureTestExt: Future {
14     /// Asserts that the given is not moved after being polled.
15     ///
16     /// A check for movement is performed each time the future is polled
17     /// and when `Drop` is called.
18     ///
19     /// Aside from keeping track of the location at which the future was first
20     /// polled and providing assertions, this future adds no runtime behavior
21     /// and simply delegates to the child future.
assert_unmoved(self) -> AssertUnmoved<Self> where Self: Sized,22     fn assert_unmoved(self) -> AssertUnmoved<Self>
23     where
24         Self: Sized,
25     {
26         AssertUnmoved::new(self)
27     }
28 
29     /// Introduces one [`Poll::Pending`](futures_core::task::Poll::Pending)
30     /// before polling the given future.
31     ///
32     /// # Examples
33     ///
34     /// ```
35     /// use futures::task::Poll;
36     /// use futures::future::FutureExt;
37     /// use futures_test::task::noop_context;
38     /// use futures_test::future::FutureTestExt;
39     /// use futures::pin_mut;
40     ///
41     /// let future = (async { 5 }).pending_once();
42     /// pin_mut!(future);
43     ///
44     /// let mut cx = noop_context();
45     ///
46     /// assert_eq!(future.poll_unpin(&mut cx), Poll::Pending);
47     /// assert_eq!(future.poll_unpin(&mut cx), Poll::Ready(5));
48     /// ```
pending_once(self) -> PendingOnce<Self> where Self: Sized,49     fn pending_once(self) -> PendingOnce<Self>
50     where
51         Self: Sized,
52     {
53         PendingOnce::new(self)
54     }
55 
56     /// Runs this future on a dedicated executor running in a background thread.
57     ///
58     /// # Examples
59     ///
60     /// ```
61     /// # futures::executor::block_on(async {
62     /// use futures::channel::oneshot;
63     /// use futures_test::future::FutureTestExt;
64     ///
65     /// let (tx, rx) = oneshot::channel::<i32>();
66     ///
67     /// (async { tx.send(5).unwrap() }).run_in_background();
68     ///
69     /// assert_eq!(rx.await, Ok(5));
70     /// # });
71     /// # std::thread::sleep(std::time::Duration::from_millis(500)); // wait for background threads closed: https://github.com/rust-lang/miri/issues/1371
72     /// ```
run_in_background(self) where Self: Sized + Send + 'static, Self::Output: Send,73     fn run_in_background(self)
74     where
75         Self: Sized + Send + 'static,
76         Self::Output: Send,
77     {
78         thread::spawn(|| futures_executor::block_on(self));
79     }
80 
81     /// Introduces an extra [`Poll::Pending`](futures_core::task::Poll::Pending)
82     /// in between each call to poll.
83     ///
84     /// # Examples
85     ///
86     /// ```
87     /// use futures::task::Poll;
88     /// use futures::future::{self, Future};
89     /// use futures_test::task::noop_context;
90     /// use futures_test::future::FutureTestExt;
91     /// use futures::pin_mut;
92     ///
93     /// let future = future::ready(1).interleave_pending();
94     /// pin_mut!(future);
95     ///
96     /// let mut cx = noop_context();
97     ///
98     /// assert_eq!(future.as_mut().poll(&mut cx), Poll::Pending);
99     /// assert_eq!(future.as_mut().poll(&mut cx), Poll::Ready(1));
100     /// ```
interleave_pending(self) -> InterleavePending<Self> where Self: Sized,101     fn interleave_pending(self) -> InterleavePending<Self>
102     where
103         Self: Sized,
104     {
105         InterleavePending::new(self)
106     }
107 }
108 
109 impl<Fut> FutureTestExt for Fut where Fut: Future {}
110