1//! Additional combinators for testing futures.
2
3mod pending_once;
4pub use self::pending_once::PendingOnce;
5
6use futures_core::future::Future;
7use std::thread;
8
9pub use crate::assert_unmoved::AssertUnmoved;
10pub use crate::interleave_pending::InterleavePending;
11
12/// Additional combinators for testing futures.
13pub 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.
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 /// ```
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 /// ```
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 /// ```
101 fn interleave_pending(self) -> InterleavePending<Self>
102 where
103 Self: Sized,
104 {
105 InterleavePending::new(self)
106 }
107}
108
109impl<Fut> FutureTestExt for Fut where Fut: Future {}
110