tests: document and check for ab(1) dependency

ab(1) is less common than our other dependencies, so allow tests
to run without it.

1 files changed, 1 insertions, 0 deletions

diff --git a/HACKING b/HACKING
index a58c7e8..99cd3c3 100644
--- a/HACKING
+++ b/HACKING
@@ -4,6 +4,7 @@ development dependencies
 * minitest RubyGem (version 4 or 5, standard in Ruby 2.0+)
 * curl - http://curl.haxx.se/ - we don't trust our own Ruby abilities :>
 * dd(1) - standard POSIX tool - to feed curl
+* ab - http://httpd.apache.org - for concurrent testing
 * GNU make - https://www.gnu.org/software/make/
 * git - http://www.git-scm.com/
 * ruby - http://www.ruby-lang.org/