% bundle exec rake test TEST="test/unit/foreman/http_proxy_test.rb" 
The Apipie cache is turned off. Enable it and run apipie:cache rake task to speed up API calls.
Run options: --seed 37549

# Running:

.....E

Error:
HTTPProxyTest::Excon::Connection extension#test_0002_rescues requests and mentions proxy:
SystemStackError: stack level too deep
    test/unit/foreman/http_proxy_test.rb:120:in `block (2 levels) in <class:HTTPProxyTest>'
    test/test_helper.rb:68:in `before_setup'

bin/rails test test/unit/foreman/http_proxy_test.rb:130

E

Error:
HTTPProxyTest::Excon::Connection extension#test_0001_set @data[:proxy] to proxy:
SystemStackError: stack level too deep
    test/unit/foreman/http_proxy_test.rb:120:in `block (2 levels) in <class:HTTPProxyTest>'
    test/test_helper.rb:68:in `before_setup'

bin/rails test test/unit/foreman/http_proxy_test.rb:124

...............

Finished in 1.127359s, 19.5146 runs/s, 20.4017 assertions/s.
22 runs, 23 assertions, 0 failures, 2 errors, 0 skips

downgrading mocha to 1.9.0 fixes the issue