##How the project was created
###Created umbrella app
mix new mix_test_umbrella --umbrella
###Created 2 phoenix apps under the umbrella
cd mix_test_umbrella/apps
mix phoenix.new api --no-html --no-brunch
mix phoenix.new web --no-html --no-brunch
##How to make it fail
###Run mix test from the parent
git clone https://github.com/chrisfishwood/mix_test_umbrella.git
cd mix_test_umbrella
mix test
The api application will pass, the web application will fail with database "web_test" does not exist.