Fix JS tests

package-lock.json

@@ -0,0 +1,11 @@
+{
+  "requires": true,
+  "lockfileVersion": 1,
+  "dependencies": {
+    "prettier": {
+      "version": "1.18.2",
+      "resolved": "https://registry.npmjs.org/prettier/-/prettier-1.18.2.tgz",
+      "integrity": "sha512-OeHeMc0JhFE9idD4ZdtNibzY0+TPHSpSSb9h8FqtP+YnoZZ1sl8Vc9b1sasjfymH3SonAF4QcA2+mzHPhMvIiw=="
+    }
+  }
+}

webext/test/helper.js

@@ -40,6 +40,11 @@ global.dimensions = {
 
 global.document = {
   addEventListener: () => {},
+  body: {
+    contains: () => {
+      return true;
+    }
+  },
   getElementById: () => {},
   getElementsByTagName: () => {
     return [
@@ -135,7 +140,12 @@ let functions = {
     let text_builder = new TextBuilder(
       channel,
       graphics_builder.dimensions,
-      graphics_builder
+      graphics_builder,
+      {
+        browsh: {
+          use_experimental_text_visibility: true
+        }
+      }
     );
     graphics_builder._getScreenshotWithText(() => {
       graphics_builder._getScreenshotWithoutText();