diff --git a/main.go b/main.go
index 2c669e322f..32f011e917 100644
--- a/main.go
+++ b/main.go
@@ -6,9 +6,7 @@ import (
 	"github.com/golang/protobuf/proto"
 	"github.com/ry/v8worker2"
 	"log"
-	"net/url"
 	"os"
-	"path"
 	"runtime/pprof"
 )
 
@@ -21,26 +19,6 @@ var DenoDir string
 var CompileDir string
 var SrcDir string
 
-func ResolveModule(moduleSpecifier string, containingFile string) (
-	moduleName string, filename string, err error) {
-	moduleUrl, err := url.Parse(moduleSpecifier)
-	if err != nil {
-		return
-	}
-	baseUrl, err := url.Parse(containingFile)
-	if err != nil {
-		return
-	}
-	resolved := baseUrl.ResolveReference(moduleUrl)
-	moduleName = resolved.String()
-	if moduleUrl.IsAbs() {
-		filename = path.Join(SrcDir, resolved.Host, resolved.Path)
-	} else {
-		filename = resolved.Path
-	}
-	return
-}
-
 func stringAsset(path string) string {
 	data, err := Asset("dist/" + path)
 	check(err)
diff --git a/os.go b/os.go
index 59c24ccdff..44ec2ba9c2 100644
--- a/os.go
+++ b/os.go
@@ -3,7 +3,9 @@ package main
 import (
 	"github.com/golang/protobuf/proto"
 	"io/ioutil"
+	"net/url"
 	"os"
+	"path"
 	"strings"
 )
 
@@ -31,6 +33,26 @@ func InitOS() {
 	})
 }
 
+func ResolveModule(moduleSpecifier string, containingFile string) (
+	moduleName string, filename string, err error) {
+	moduleUrl, err := url.Parse(moduleSpecifier)
+	if err != nil {
+		return
+	}
+	baseUrl, err := url.Parse(containingFile)
+	if err != nil {
+		return
+	}
+	resolved := baseUrl.ResolveReference(moduleUrl)
+	moduleName = resolved.String()
+	if moduleUrl.IsAbs() {
+		filename = path.Join(SrcDir, resolved.Host, resolved.Path)
+	} else {
+		filename = resolved.Path
+	}
+	return
+}
+
 func HandleSourceCodeFetch(moduleSpecifier string, containingFile string) (out []byte) {
 	assert(moduleSpecifier != "", "moduleSpecifier shouldn't be empty")
 	res := &Msg{}
diff --git a/main_test.go b/os_test.go
similarity index 100%
rename from main_test.go
rename to os_test.go