Add unit tests

src/hyperfine/benchmark.rs

@@ -8,7 +8,7 @@ use statistical::{mean, standard_deviation};
 use hyperfine::internal::{get_progress_bar, max, min, CmdFailureAction, HyperfineOptions, Second,
                           Warnings, MIN_EXECUTION_TIME};
 use hyperfine::format::{format_duration, format_duration_unit};
-use hyperfine::cputime::{get_cpu_interval, get_cpu_times};
+use hyperfine::cputime::{cpu_time_interval, get_cpu_times};
 
 /// Results from timing a single shell command
 #[derive(Debug, Copy, Clone)]
@@ -64,7 +64,7 @@ pub fn time_shell_command(
     let mut time_real = duration.as_secs() as f64 + (duration.subsec_nanos() as f64) * 1e-9;
 
     // User and system time
-    let cpu_interval = get_cpu_interval(&start_cpu, &end_cpu);
+    let cpu_interval = cpu_time_interval(&start_cpu, &end_cpu);
     let mut time_user = cpu_interval.user;
     let mut time_system = cpu_interval.system;
 

src/hyperfine/cputime.rs

@@ -21,7 +21,7 @@ pub struct CPUInterval {
     pub system: Second,
 }
 
-/// Read CPU execution times (user and system time) from kernel
+/// Read CPU execution times ('user' and 'system')
 pub fn get_cpu_times() -> CPUTimes {
     let result: rusage = unsafe {
         let mut buf = mem::zeroed();
@@ -30,20 +30,45 @@ pub fn get_cpu_times() -> CPUTimes {
         buf
     };
 
-    const USEC_PER_SEC: i64 = 1000 * 1000;
+    const MICROSEC_PER_SEC: i64 = 1000 * 1000;
 
     CPUTimes {
-        user_usec: i64::from(result.ru_utime.tv_sec) * USEC_PER_SEC
+        user_usec: i64::from(result.ru_utime.tv_sec) * MICROSEC_PER_SEC
             + i64::from(result.ru_utime.tv_usec),
-        system_usec: i64::from(result.ru_stime.tv_sec) * USEC_PER_SEC
+        system_usec: i64::from(result.ru_stime.tv_sec) * MICROSEC_PER_SEC
             + i64::from(result.ru_stime.tv_usec),
     }
 }
 
-/// Compute the time intervals in between two CPUTimes snapshots
-pub fn get_cpu_interval(start: &CPUTimes, end: &CPUTimes) -> CPUInterval {
+/// Compute the time intervals in between two `CPUTimes` snapshots
+pub fn cpu_time_interval(start: &CPUTimes, end: &CPUTimes) -> CPUInterval {
     CPUInterval {
         user: ((end.user_usec - start.user_usec) as f64) * 1e-6,
         system: ((end.system_usec - start.system_usec) as f64) * 1e-6,
     }
 }
+
+#[test]
+fn test_cpu_time_interval() {
+    let t_a = CPUTimes {
+        user_usec: 12345,
+        system_usec: 54321,
+    };
+
+    let t_b = CPUTimes {
+        user_usec: 20000,
+        system_usec: 70000,
+    };
+
+    let t_zero = cpu_time_interval(&t_a, &t_a);
+    assert_eq!(0.0, t_zero.user);
+    assert_eq!(0.0, t_zero.system);
+
+    let t_ab = cpu_time_interval(&t_a, &t_b);
+    assert_relative_eq!(0.007655, t_ab.user);
+    assert_relative_eq!(0.015679, t_ab.system);
+
+    let t_ba = cpu_time_interval(&t_b, &t_a);
+    assert_relative_eq!(-0.007655, t_ba.user);
+    assert_relative_eq!(-0.015679, t_ba.system);
+}

src/main.rs

@@ -5,6 +5,10 @@ extern crate indicatif;
 extern crate libc;
 extern crate statistical;
 
+#[cfg(test)]
+#[macro_use]
+extern crate approx;
+
 use std::cmp;
 use std::error::Error;
 use std::io;