1 /*!
2 Using `env_logger` in tests.
3 
4 Log events will be captured by `cargo` and only printed if the test fails.
5 You can run this example by calling:
6 
7 ```text
8 cargo test --example in_tests
9 ```
10 
11 You should see the `it_does_not_work` test fail and include its log output.
12 */
13 
main()14 fn main() {}
15 
16 #[cfg(test)]
17 mod tests {
18     use log::debug;
19 
init_logger()20     fn init_logger() {
21         let _ = env_logger::builder()
22             // Include all events in tests
23             .filter_level(log::LevelFilter::max())
24             // Ensure events are captured by `cargo test`
25             .is_test(true)
26             // Ignore errors initializing the logger if tests race to configure it
27             .try_init();
28     }
29 
30     #[test]
it_works()31     fn it_works() {
32         init_logger();
33 
34         let a = 1;
35         let b = 2;
36 
37         debug!("checking whether {} + {} = 3", a, b);
38 
39         assert_eq!(3, a + b);
40     }
41 
42     #[test]
it_does_not_work()43     fn it_does_not_work() {
44         init_logger();
45 
46         let a = 1;
47         let b = 2;
48 
49         debug!("checking whether {} + {} = 6", a, b);
50 
51         assert_eq!(6, a + b);
52     }
53 }
54