Hashicups data sources

I’m working my way through the hashicups tutorial using the provider plugin framework. When I get to the end of the data sources section and I run terraform plan the only output I get is

Changes to Outputs:
  + edu_coffees = {}

but according the example I see

Changes to Outputs:
  + edu_coffees = {
      + coffees = [
          + {
              + description = ""
              + id          = 1
              + image       = "/hashicorp.png"
              + ingredients = [
                  + {
                      + id = 6
                    },
                ]
              + name        = "HCP Aeropress"
              + price       = 200
              + teaser      = "Automation in a cup"
            },
#...

Am I doing something wrong?

Looking at the logs of the api server I would expect the /coffees endpoint to get called, but it doesn’t, only /signin.