add db mock

jest-mongodb-config.js

@@ -0,0 +1,12 @@
+module.exports = {
+    mongodbMemoryServerOptions: {
+        binary: {
+            version: '4.0.3',
+            skipMD5: true
+        },
+        instance: {
+            dbName: 'jest'
+        },
+        autoStart: false
+    }
+};