See:

• Cloud Functions Hello World tutorial
• Cloud Functions Hello World sample source code

See the Cloud Functions Hello World tutorial.

Note: in order for the tests to run properly, you'll have to deploy some of the sample functions:

gcloud functions deploy helloHttp --runtime nodejs8 --trigger-http
gcloud functions deploy helloPubSub --trigger-topic $FUNCTIONS_TOPIC --runtime nodejs8
gcloud functions deploy helloGCS --runtime nodejs8 --trigger-resource $FUNCTIONS_DELETABLE_BUCKET --trigger-event providers/cloud.storage/eventTypes/object.change

1. Read and follow the prerequisites.

2. Install dependencies:

    npm install
   

3. Set the following environment variables:

    export GCF_REGION=us-central1
    export FUNCTIONS_TOPIC=[YOUR_PUBSUB_TOPIC]
    export FUNCTIONS_DELETABLE_BUCKET=[YOUR_CLOUD_STORAGE_BUCKET]  # will be deleted by tests!
   

4. Run the tests:

    npm test