fix: mongoose 5.2.0 now uses countDocuments instead of count

See 
Automattic/mongoose@93d06a4

Closes #108

Author: nodkz

src/__mocks__/mongooseCommon.js

@@ -15,7 +15,7 @@ mongoose.connect = (async () => {
   const mongoUri = await mongoServer.getConnectionString(true);
 
   // originalConnect.bind(mongoose)(mongoUri, { useMongoClient: true }); // mongoose 4
-  originalConnect.bind(mongoose)(mongoUri); // mongoose 5
+  originalConnect.bind(mongoose)(mongoUri, { useNewUrlParser: true }); // mongoose 5
 
   mongoose.connection.on('error', e => {
     if (e.message.code === 'ETIMEDOUT') {

src/resolvers/count.js

@@ -33,7 +33,13 @@ export default function count(
     resolve: (resolveParams: ExtendedResolveParams) => {
       resolveParams.query = model.find();
       filterHelper(resolveParams);
-      return resolveParams.query.count().exec();
+      if (resolveParams.query.countDocuments) {
+        // mongoose 5.2.0 and above
+        return resolveParams.query.countDocuments().exec();
+      } else {
+        // mongoose 5 and below
+        return resolveParams.query.count().exec();
+      }
     },
   });
 }