[tests][database] add database helpers

bridge/helpers/database/index.js

@@ -0,0 +1,17 @@
+const CONTENTS = require('./content');
+
+module.exports = {
+  setDatabaseContents() {
+    const database = firebaseAdmin.database();
+    return Promise.all([
+      database.ref('tests/types').set(CONTENTS.DEFAULT),
+      database.ref('tests/priority').setWithPriority(
+        {
+          foo: 'bar',
+        },
+        666
+      ),
+      database.ref('tests/query').set(CONTENTS.QUERY),
+    ]);
+  },
+};