Use regular "go test" for unit testing. If you're using metadata inside your function (e.g., to extract an event ID) you can use metadata.NewContext to pass into your function while testing: https://godoc.org/cloud.google.com/go/functions/metadata#New...

If you just want to execute your function, create another package main and start an HTTP server, as you'd normally do.

There are some examples on this page: https://cloud.google.com/functions/docs/bestpractices/testin...

We're thinking about ways to improve the local development/testing story, and are keen to hear any ideas/feedback.

Disclaimer: I work at Google, and worked on this product.