Working example using MockPass, a mock SingPass/CorpPass server and spcp-auth-client.
# Install dependencies
npm i --prefix=mockpass
npm i
# Starts MockPass
npm start --prefix mockpass
# Starts Client
npm run dev
# Go to http://localhost:5000/private
# See Hello World in browser.Compount Launch Configurations can be used to start debug sesssions for Client and MockPass in parallel.
Breakpoints can be set in mockpass\node_modules\@opengovsg\mockpass\lib\express\spcp.js understand SingPass authentication flow.