I have always wanted to have some fun with Minitest but until this weekend I never got the chance to do it. For those of you that don’t know, Minitest is a suite of testing facilities, that support TDD, BDD, mocking and benchmarking. Having wanted to play with Minitest, this weekend I decided that I will migrate the test suite of a gem of mine, from RSpec to Minitest. Read on to see how it all went.
The gem that I worked with is called Forecastr. It is a very minimal gem that serves as a wrapper for the Open Weather Map API. It supports only current forecast: temperature, pressure, humidity, min/max temperatures and wind (speed and direction).
After checking out to a new Git branch (duh!) I first went to the gemspec and changed the RSpec dependency to Minitest.
Setup-wise, the first difference that I noticed is that while RSpec’s specs
spec/forecastr, Minitest’s tests live in
Although this is the default, it’s not the only way to do it. When creating the
new Rake task for running the Minitest tests, which I’ll get to shortly, one
can specify the path where she/he wants the tests to live.
In the newly created
test/forecastr path, I had to add the
The purpose of the file is the same as
spec_helper.rb in RSpec. Instead of
requiring RSpec, now I had to require:
The last important thing was the Rake task. To run all the tests one needs to add a built-in Rake task to the Rakefile:
Rake::TestTask object is the task that will be called when running
rake test in command line. As you can see, it takes a small configuration block. In
it, one can set the path of the tests (what I mentioned before). On the last
line, I made this task to be the default one, because it’s more convenient for
me and I don’t need to run any other tasks.
The first test
I started by migrating one test at a time from the spec directory to the test
directory. What was interesting to me is that every test file in Minitest is a
class that inherits from
Minitest::Test. Also, every test case is a
method, which of course makes sense since the test file is a class. In contrast
to RSpec, Minitest is very verbose, while RSpec hides a lot of complexity for
you with it’s huge collection of helper methods.
At the beginning I had a bit of problem with naming the methods because I was used to the “free text” way of describing test cases in RSpec. I eventually got the first one:
What was interesting to me is that I got really cool warnings when running the tests:
The reason behind these errors is that, back in the day when I was writing the
I had added
direction. Although I had these
in place, I had overridden the methods, so the warning was spot on.
After removing the unneeded attr_readers the warnings went away.
Although this is a nice feature of Minitest, I ended up turning it off because it started reporting warnings for libraries that weren’t under my control:
After some fun with the test, I got it passing:
After migrating two classes from RSpec to Minitest, I noticed a change in my
workflow. I was running
rake, which runs the complete suite, to run just
one test. The only way I could find to run a single test seems a bit too
verbose for me. Since I am very used to RSpec, running a test with the line
number is one of my most used features of RSpec.
In this sense, Minitest gave me a tiny disappointment. Running a huge command with four arguments every time I want to run a single test is a flow-killer. True, I could use Guard to run the test when it gets changed. But also, I often want to run tests by hand without any hassle.
Thanks to Nick Quaranto who wrote the m gem. The gem is quite simple - just a Test::Unit runner that can run tests by line number. Although simple, it is exactly what I needed!
This means that, instead of running a single test with:
m allowes one to do the same with:
After getting all my tests green, I took a look at Minitest’s Spec DSL. Mintest::Spec is a functionally complete spec engine. It turns the test assertions into spec expectations. This basically allows the developers to use Minitest just as RSpec. The syntax is pretty much the same, so migrating RSpec suite to Minitest is much much easier with Minitest::Spec in the mix.
My personal preference in this case was to stay away from spec expectations and think more in a test assertions way. Although they are basically the same, this experience was much more joyful for me. Or maybe I just needed to have fun with something new.
The basic output, or the one that comes with
minitest/pride wasn’t really
cutting it for me. When looking for other formatting options, I ran into
minitest-reporters - a gem for
creating customizable Minitest output formats.
The setup is quite easy - just require the library in the
The gem has couple of built-in reporters, and I went for the
Minitest::Reporters::SpecReporter. With this gem one can also create his
own reporters and formatting.
So, what’s next?
Although Forecastr’s codebase might not be big with lots of challenges in it, this was defnitely a really nice exercise for a hot Saturday afternoon. I just wish I had the chance to work with Fixtures and some fake objects.
All in all, what I can say now is that using Minitest was a real joy. It seems to be very simple to setup, extend and use. But, although simple, in my opinion it is as powerful as the other alternatives.
You can see the whole RSpec to Minitest migration on this commit.