Fix MonotonicTime::elapsed()

Author: andrei-21

lightning/src/util/time.rs

@@ -89,7 +89,7 @@ impl Time for MonotonicTime {
 	}
 
 	fn elapsed(&self) -> Duration {
-		self.0.elapsed()
+		Self::now().0 - self.0
 	}
 }
 
@@ -180,7 +180,10 @@ pub mod tests {
 	#[cfg(not(feature = "no-std"))]
 	fn monotonic_time_go_backward() {
 		let now = super::MonotonicTime::now();
+		assert!(now.elapsed() < Duration::from_secs(10));
+
 		let ten_years = Duration::from_secs(10 * 365 * 24 * 60 * 60);
-		let _past = now - ten_years;
+		let past = now - ten_years;
+		assert!(past.elapsed() >= ten_years);
 	}
 }