diff --git a/credentials_test.go b/credentials_test.go
new file mode 100644
index 0000000..e14256b
--- /dev/null
+++ b/credentials_test.go
@@ -0,0 +1,24 @@
+package socks5
+
+import (
+	"testing"
+)
+
+func TestStaticCredentials(t *testing.T) {
+	creds := StaticCredentials{
+		"foo": "bar",
+		"baz": "",
+	}
+
+	if !creds.Valid("foo", "bar") {
+		t.Fatalf("expect valid")
+	}
+
+	if !creds.Valid("baz", "") {
+		t.Fatalf("expect valid")
+	}
+
+	if creds.Valid("foo", "") {
+		t.Fatalf("expect invalid")
+	}
+}