Coveralls is a service that keep track of your tests coverage
for you. It can notifies you when your coverage decreases under a custom
threshold, and their bot comments on pull requests to report their tests
coverage. Like Travis-CI, it allows you to add a badge to your readme with
an up-to-date tests coverage percentage.
If you already test your GitHub projects with a CI server like Travis, it’s
very easy to add Coveralls to your workflow. Unfortunately, they have a library
for Ruby, a couple user-provided libraries for other languages such as PHP,
Java and Python, but nothing for Clojure. Fortunately, they provide an API for
unsupported languages like Clojure. Here is how to use it.
Cloverage
Cloverage is a Clojure library and a Leiningen plugin to get
form-level tests coverage of your projects. It’s dead easy to use and generates
HTML reports for you as well as some other formats.
Add their plugin to your project.clj:
(defproject your-project "0.1.0"
; ...
:plugins [[lein-cloverage "1.0.2"]])
Use lein cloverage to run your tests and generate various reports. You can
specify which Cloverage version you want to use with CLOVERAGE_VERSION. The
latest stable one is 1.0.3, but we’ll need to use 1.0.4-SNAPSHOT for this
article:
CLOVERAGE_VERSION=1.0.4-SNAPSHOT lein cloverage
Coveralls
If you don’t already use it, signup on Coveralls using your GitHub account.
Then, click on “Add Repo”, find your repo in the list and activate it. That’s
all you have to do on their website for now.
Travis CI
You now need to custom your builds on Travis to use Coveralls. We’ll do it in a
Bash script, so add this to your .travis.yml:
after_script:
- bash -ex test/coveralls.sh
This tells Travis to run test/coveralls.sh after each build. We use Bash
options -e and -x to respectively stop the script at the first failure and
print each command.
Now edit test/coveralls.sh and add the following content:
COVERALLS_URL='https://coveralls.io/api/v1/jobs'
CLOVERAGE_VERSION='1.0.4-SNAPSHOT' lein2 cloverage -o cov --coveralls
curl -F 'json_file=@cov/coveralls.json' "$COVERALLS_URL"
It’ll run Cloverage and output reports in cov (use another name if you
prefer), using a report for Coveralls. This generates a coveralls.json file
which can then be sent to their API. That’s what we do on the next line, using
cURL.
That’s all! You can now push on GitHub, Travis will run your tests and send
their tests coverage to Coveralls.
Caveats
Coveralls doesn’t support partial-line tests coverage, so we’re cheating a
little bit here using hits count. A line that it never covered has 0 hits, one
that is partially covered has one hit, and a fully covered one has two hits.
There’s an open issue regarding this.
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Black-box testing is a method of software testing that examines the
functionality of an application (e.g. what the software does) without peering
into its internal structures or workings
(Wikipedia). While it’s
usually done at a system level, I think the most obvious place it should be
used is at the function level. It’s even more efficient if you write tests for
someone else’s code.
Here is how I write unit tests for functions.
Good Names
If you can’t tell what the function roughly does only by looking at its name,
it’s usually because it’s badly named or it’s doing too many things, maybe you
should break it in smaller functions. Look at its arguments names. Do they make
sense to you? Do you understand what’s the function doing only by looking as
its name and its arguments?
Good Documentation
You sometimes need to read a function’s documentation if its name is unclear or
if it’s a complicated code area. This is your latest chance to understand the
function, because in function-level black-box testing you can’t read the code,
it would not be black-box anymore. If you understand the function, you can now
write tests. If not, you should improve its name, its arguments names, and its
documentation, in that order because it’s the order one reads it.
Good Tests
Good unit tests are short, incremental, and test only a specific case. Start
with the simplest. Does the function takes a string? Give it an empty one. Does
it take a number? Give it 0. Use null for objects. Then move to more edge
cases: negative numbers, un-trimmed strings, uninitialized objects. Add more
simple edge cases, but only once at a time. Then, combine those edge cases.
Write more complex cases. Never combine two cases you never individually tested
before. After all these edge cases, test the legitimate ones. Again start with
the simplest, then add more complexity and combine cases.
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I discovered a great feature in Vim today. While we generally
use the same Vim settings everywhere, we sometimes (have to) contribute to
projects with a coding style different of ours, and because nobody wants to
edit their .vimrc everytime to switch between configurations, Vim allows you
to have per project .vimrc’s.
This feature can be enabled with one line in your .vimrc:
When you start Vim, it begins by looking at some predefined locations for a
configuration file (the first one is $HOME/.vimrc). The exrc option,
disabled by default, tell to Vim to not only load your personal .vimrc, but
also to look in the current directory to check if there’s another .vimrc file,
which will be loaded after your personal one. You can then use it to override
your settings and/or add specific ones for this directory.
Additionally, if you share the local .vimrc with others (e.g. in a Git
repository), you may want to set the secure option at the end of your personal
.vimrc:
This disallow shell and write commands in the .vimrc of the local directory.
On unix-like OSes, this option is set by default if
you’re not the owner of the file.
For more Vim gems, check my .vimrc on GitHub!
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