use init function

a_test.go

@@ -1,10 +0,0 @@
-package docker
-
-import (
-	"os"
-	"testing"
-)
-
-func Test(t *testing.T) {
-	os.Setenv("TEST", "1")
-}

runtime_test.go

@@ -72,6 +72,8 @@ func layerArchive(tarfile string) (io.Reader, error) {
 }
 
 func init() {
+	os.Setenv("TEST", "1")
+
 	// Hack to run sys init during unit testing
 	if selfPath := utils.SelfPath(); selfPath == "/sbin/init" || selfPath == "/.dockerinit" {
 		SysInit()