package runtime_test

import (
	"runtime"
	"testing"
)

func TestGcSys(t *testing.T) {
	runtime.GC()
	runtime.UpdateMemStats()
	sys := runtime.MemStats.Sys

	for i := 0; i < 1000000; i++ {
		workthegc()
	}

	// Should only be using a few MB.
	runtime.UpdateMemStats()
	if sys > runtime.MemStats.Sys {
		sys = 0
	} else {
		sys = runtime.MemStats.Sys - sys
	}
	t.Logf("used %d extra bytes", sys)
	if sys > 4<<20 {
		t.Fatalf("using too much memory: %d bytes", sys)
	}
}

func workthegc() []byte {
	return make([]byte, 1029)
}