Fix JRuby Sinatra Integration Test

[ivanovac]

Problem

The JRuby Sinatra integration test (TestIntegration/integration/Default/jruby/builds_and_runs_the_jruby_sinatra_app) was consistently failing with the following symptoms:

• Application staging completed successfully

• All dependencies (JRuby 9.4.8.0, gems) installed correctly

• App crashed during startup with health check timeout errors:
  Timed out after 1m0s (30 attempts) waiting for startup check to succeed: failed to make TCP connection to 10.255.255.77:8080: connect: connection refused

• The app logged "Invoking start command" but never actually listened on port 8080

Root Cause

The default rackup command (generated by the Ruby buildpack for Rack applications) binds only to localhost by default. In Cloud Foundry's container environment, the health check system and router need to connect from outside the container, requiring the application to bind to 0.0.0.0 (all interfaces).

While this works fine for regular Ruby/MRI applications (likely due to differences in how the Ruby runtime handles network binding), JRuby's behavior requires explicit host specification.

Solution

Added a Procfile to the fixtures/default/sinatra_jruby/ test fixture with an explicit start command:

web: bundle exec rackup config.ru -o 0.0.0.0 -p $PORT

The [-o 0.0.0.0] flag ensures the application binds to all network interfaces, allowing Cloud Foundry's health checks and routing to function properly.

Testing

• Test now passes consistently
• Application starts successfully and responds to HTTP requests
• Health checks pass on all retry attempts
• App correctly returns "jruby 3.1.4" at the /ruby endpoint

[tnikolova82]

LGTM