ERROR: There are no scenarios； must have at least one.

system:

Ubuntu 18.04

Question 1

ERROR: There are no scenarios； must have at least one.

solution

You’ve got the wrong yarn. The yarn you’re executing comes from the cmdtest package. Uninstalling cmdtest first should fix this:

sudo apt remove cmdtest

Once you’ve uninstalled it, run the commands below to install yarn properly:

curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
sudo apt update
sudo apt install yarn

From: https://stackoverflow.com/a/60016407/2193455

Question 2

info There appears to be trouble with your network connection. Retrying...

solution

yarn config set proxy http://127.0.0.1:10809
yarn config set https-proxy http://127.0.0.1:10809