[RUST] How to test println?
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// ❌ not testable | |
fn greeting_hard_to_test(nb: i32, name: &str) { | |
for _ in 0..nb { | |
println!("hi {}", name); | |
} | |
} | |
// ✅ easy to test | |
trait Logger { | |
fn log(&mut self, value: String); | |
} | |
struct ConsoleLogger; | |
impl Logger for ConsoleLogger { | |
fn log(&mut self, value: String) { | |
println!("{}", value); | |
} | |
} | |
fn greeting(nb: i32, name: &str, logger: &mut dyn Logger) { | |
for _ in 0..nb { | |
logger.log(format!("hi {}", name)); | |
} | |
} | |
#[cfg(test)] | |
mod tests { | |
use super::*; | |
#[derive(Default)] | |
struct TestLogger(Vec<String>); | |
impl Logger for TestLogger { | |
fn log(&mut self, value: String) { | |
self.0.push(value); | |
} | |
} | |
#[test] | |
fn greeting_test() { | |
let mut test_logger = TestLogger::default(); | |
greeting(2, "maxday", &mut test_logger); | |
assert_eq!(2, test_logger.0.len()); | |
assert_eq!("hi maxday", test_logger.0[0]); | |
assert_eq!("hi maxday", test_logger.0[1]); | |
} | |
} |
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