Shut Those Pesky Warnings Off in Ruby Tests

Here’s a simple fix for a minor annoyance in your Ruby environment.

I have some tests that rely on an external gem, and that gem has some deprecation warnings that have been fixed on master but not released in a new version yet. Since my app is in production, I don’t want to use an unreleased (and possibly buggy) version of a gem just to get rid of some deprecation warnings.

Even so, I get tired of seeing 50+ lines of warnings every time I run my test suite.

Niftily enough, there’s an envar I can set on each spec run that will silence these warnings:

RUBYOPT="-W0" rspec

(Tested working on my machine running Ruby 2.2.x, and according to this StackOverflow post, it also works on 2.1.x, 2.14.x, and 2.3.x.)

Great, it works! But… how?

In my Googling, I found little info about RUBYOPT. One documentation page defined it thus:

Command-line options passed to Ruby interpreter. Ignored in taint mode (Where $SAFE is greater than 0).

Okay… Kind of helpful. So, it seems to me that whatever is stored in RUBYOPT gets run as a flag on the Ruby program (in my case, rspec).

More digging found some official Ruby documentation about flags, but did not include -W0. However, this helpful StackOverflow post tells the story. It appears that -W works the same as -w in that it enables verbose mode. The difference is that the capital -W can then be further configured for exactly how verbose we want the logs to be.

• -W0 don’t show any warnings.
• -W1 show some warnings, but not Kernel warnings.
• -W2 show all warnings (-W3 and upward seem to do the same thing)

Enjoy some quieter logs! (Or louder, if that’s your thing.)