soft_test_failures/
lib.rs

1//! This crate trackes assertions during the execution of a test, delaying panicks until the end of execution.
2//! This ensures that if two assertions were to fail, the first does not clobber the second. This is most useful
3//! when writing large tests with many assertions that may begin to fail simultaneously, as you can pinpoint exactly
4//! which ones failed.
5//!
6//! # Usage
7//!
8//! Replace your normal `assert!()` assertions with `expect!()` from this crate. At the end of your test, call `let_fail!()`
9//!
10//! ```rust
11//! #[test]
12//! fn expect_failures() {
13//!     let x = 4;
14//!     let y = "is not";
15//!     let z = 5;
16//!     expect!(2 + 2 == 5, "{} surely {} {}", x, y, z);
17//!     expect!(1 + 1 == 2);
18//!     expect!(3 - 7 == -4);
19//!     expect!(3 - 7 == -3);
20//!     let_fail!();
21//! }
22//! ```
23
24use std::cell::RefCell;
25use std::thread_local;
26
27thread_local! {
28    /// Implementation detail; don't use directly
29    #[doc(hidden)]
30    pub static FAILURES: RefCell<Vec<String>> = RefCell::new(Vec::new());
31}
32
33/// Tracks a failed condition like an assertion, but allows test execution to continue.
34#[macro_export]
35macro_rules! expect {
36    ($cond:expr) => {{
37        expect!($cond, "Expected {}", stringify!($cond));
38    }};
39    ($cond:expr, $($arg:tt)+) => {{
40        if !($cond) {
41            $crate::FAILURES.with(|cell| cell.borrow_mut().push(format!($($arg)*)));
42        }
43    }};
44}
45
46/// Panics if at least one `expect!()` failed, thus failing the test.
47#[macro_export]
48macro_rules! let_fail {
49    () => {
50        use std::fmt::Write;
51        $crate::FAILURES.with(|cell| {
52            let f = cell.borrow_mut();
53            if f.len() > 0 {
54                let mut msg = format!("`expect` test failed with {} failed assertions:\n", f.len());
55                f.iter()
56                    .enumerate()
57                    .for_each(|x| writeln!(msg, "{}: {}", x.0 + 1, x.1).unwrap()); // <String as Write> never panics
58                panic!(msg);
59            } else {
60                println!("`expect` test passed.");
61            }
62        });
63    };
64}
65
66#[test]
67#[should_panic]
68fn expect_failures() {
69    let x = 4;
70    let y = "is not";
71    let z = 5;
72    expect!(2 + 2 == 5, "{} surely {} {}", x, y, z);
73    expect!(1 + 1 == 2);
74    expect!(3 - 7 == -4);
75    expect!(3 - 7 == -2);
76    let_fail!();
77}
78
79#[test]
80fn expect_pass() {
81    let x = 4;
82    let y = "is not";
83    let z = 5;
84    expect!(2 + 2 == 4, "{} surely {} {}", x, y, z);
85    expect!(1 + 1 == 2);
86    expect!(3 - 7 == -4);
87    expect!(3 - 7 == -4);
88    let_fail!();
89}
soft_test_failures/lib.rs

soft_test_failures/
lib.rs
