v/vlib/time/stopwatch_test.v

import time

// NB: on CI jobs, especially msvc ones, sleep_ms may sleep for much more
// time than you have specified. To avoid false positives from CI test
// failures, some of the asserts will be run only if you pass `-d stopwatch`
fn test_stopwatch_works_as_intended() {
	sw := time.new_stopwatch()
	// sample code that you want to measure:
	println('Hello world')
	time.sleep_ms(1)
	//
	println('Greeting the world took: ${sw.elapsed().nanoseconds()}ns')
	assert sw.elapsed().nanoseconds() > 0
}

fn test_stopwatch_time_between_pause_and_start_should_be_skipped_in_elapsed() {
	sw := time.new_stopwatch()
	time.sleep_ms(10) // A
	// eprintln('${sw.elapsed().milliseconds()}ms')
	assert sw.elapsed().milliseconds() >= 10
	sw.pause()
	time.sleep_ms(10)
	// eprintln('${sw.elapsed().milliseconds()}ms')
	assert sw.elapsed().milliseconds() >= 10
	$if stopwatch ? {
		assert sw.elapsed().milliseconds() < 20
	}
	sw.start()
	time.sleep_ms(10) // B
	// Here, sw.elapsed() should be ~10ms (from A) + ~10ms (from B) >= 20ms
	assert sw.elapsed().milliseconds() >= 20
	$if stopwatch ? {
		assert sw.elapsed().milliseconds() < 30
	}
}