diff --git a/integration_test.go b/integration_test.go
index f1a60f499d..90aad560b5 100644
--- a/integration_test.go
+++ b/integration_test.go
@@ -12,6 +12,8 @@ import (
 	"testing"
 )
 
+var denoFn string
+
 // Some tests require an HTTP server. We start one here.
 // Because we process tests synchronously in this program we must run
 // the server as a subprocess.
@@ -45,7 +47,7 @@ func listTestFiles() []string {
 	return out
 }
 
-func checkOutput(t *testing.T, outFile string, denoFn string) {
+func checkOutput(t *testing.T, outFile string) {
 	outFile = path.Join("testdata", outFile)
 	jsFile := strings.TrimSuffix(outFile, ".out")
 
@@ -54,19 +56,10 @@ func checkOutput(t *testing.T, outFile string, denoFn string) {
 		t.Fatal(err.Error())
 	}
 
-	dir, err := ioutil.TempDir("", "TestIntegration")
-	if err != nil {
-		panic(err)
-	}
-
-	cmd := exec.Command(denoFn, "--cachedir="+dir, jsFile)
-	var out bytes.Buffer
-	cmd.Stdout = &out
-	err = cmd.Run()
+	actual, _, err := deno(jsFile)
 	if err != nil {
 		t.Fatal(err.Error())
 	}
-	actual := out.Bytes()
 	if bytes.Compare(actual, expected) != 0 {
 		t.Fatalf(`Actual output does not match expected.
 -----Actual-------------------
@@ -75,17 +68,65 @@ func checkOutput(t *testing.T, outFile string, denoFn string) {
 	}
 }
 
-func TestIntegration(t *testing.T) {
+func deno(inputFn string) (actual []byte, cachedir string, err error) {
+	cachedir, err = ioutil.TempDir("", "TestIntegration")
+	if err != nil {
+		panic(err)
+	}
+
+	cmd := exec.Command(denoFn, "--cachedir="+cachedir, inputFn)
+	var out bytes.Buffer
+	cmd.Stdout = &out
+	err = cmd.Run()
+	if err == nil {
+		actual = out.Bytes()
+	}
+	return
+}
+
+func integrationTestSetup() {
 	startServer()
 	cwd, err := os.Getwd()
 	if err != nil {
 		panic(err)
 	}
-	denoFn := path.Join(cwd, "deno")
+	denoFn = path.Join(cwd, "deno")
+}
+
+func TestIntegration(t *testing.T) {
+	integrationTestSetup()
 	outFiles := listTestFiles()
 	for _, outFile := range outFiles {
 		t.Run(outFile, func(t *testing.T) {
-			checkOutput(t, outFile, denoFn)
+			checkOutput(t, outFile)
 		})
 	}
 }
+
+func TestUrlArgs(t *testing.T) {
+	integrationTestSetup()
+
+	// Using good port 4545
+	_, cachedir, err := deno("http://localhost:4545/testdata/001_hello.js")
+	if err != nil {
+		t.Fatalf("Expected success. %s", err.Error())
+	}
+	cacheFn := path.Join(cachedir, "src/localhost:4545/testdata/001_hello.js")
+	println("good cacheFn", cacheFn)
+	if !exists(cacheFn) {
+		t.Fatalf("Expected 200 at '%s'", cacheFn)
+	}
+	// TODO check output
+
+	// Using bad port 4546 instead of 4545.
+	_, cachedir, err = deno("http://localhost:4546/testdata/001_hello.js")
+	if err == nil {
+		t.Fatalf("Expected 404. %s", err.Error())
+	}
+	// Check that cache dir is emtpy.
+	cacheFn = path.Join(cachedir, "src/localhost:4546/testdata/001_hello.js")
+	println("bad cacheFn", cacheFn)
+	if exists(cacheFn) {
+		t.Fatalf("Expected 404 at '%s'", cacheFn)
+	}
+}
diff --git a/runtime.ts b/runtime.ts
index 9613ab117f..e95ac4b589 100644
--- a/runtime.ts
+++ b/runtime.ts
@@ -125,10 +125,10 @@ export function resolveModule(
   moduleSpecifier: string,
   containingFile: string
 ): FileModule {
+  util.log("resolveModule", { moduleSpecifier, containingFile });
   util.assert(moduleSpecifier != null && moduleSpecifier.length > 0);
   // We ask golang to sourceCodeFetch. It will load the sourceCode and if
   // there is any outputCode cached, it will return that as well.
-  util.log("resolveModule", { moduleSpecifier, containingFile });
   const { filename, sourceCode, outputCode } = os.sourceCodeFetch(
     moduleSpecifier,
     containingFile
diff --git a/util.go b/util.go
index 1871156d32..5878d87b9e 100644
--- a/util.go
+++ b/util.go
@@ -13,6 +13,18 @@ func logDebug(format string, v ...interface{}) {
 	}
 }
 
+// exists returns whether the given file or directory exists or not
+func exists(path string) bool {
+	_, err := os.Stat(path)
+	if err == nil {
+		return true
+	}
+	if os.IsNotExist(err) {
+		return false
+	}
+	panic(err)
+}
+
 func assert(cond bool, msg string) {
 	if !cond {
 		panic(msg)