time: add stopwatch_test.v

vlib/time/stopwatch_test.v

@@ -0,0 +1,28 @@
+import time
+
+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
+	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
+	assert sw.elapsed().milliseconds()	< 30
+}