diff --git a/service_test.go b/service_test.go
index 8e27b56..7304ae7 100644
--- a/service_test.go
+++ b/service_test.go
@@ -3,6 +3,7 @@
 import (
 	"net/http"
 	"net/http/httptest"
+	"os"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -51,6 +52,19 @@
 	router.ServeHTTP(w, req)
 
 	assert.Equal(t, http.StatusOK, w.Code)
+	assert.Contains(t, w.Body.String(), "data-server=\"https://korap.ids-mannheim.de\"")
+	assert.Contains(t, w.Body.String(), "<title>External Provider</title>")
+
+	os.Setenv("KORAP_SERVER", "https://korap.ids-mannheim.de/instance/test")
+
+	router = setupRouter()
+
+	w = httptest.NewRecorder()
+	req, _ = http.NewRequest(http.MethodGet, "/", nil)
+
+	router.ServeHTTP(w, req)
+
+	assert.Equal(t, http.StatusOK, w.Code)
 	assert.Contains(t, w.Body.String(), "data-server=\"https://korap.ids-mannheim.de/instance/test\"")
 	assert.Contains(t, w.Body.String(), "<title>External Provider</title>")
 }