Chapter 5: Testing
Rubyists love testing, so before we go any farther, let’s talk about testing. In Crystal, there is a testing framework built in, and it’s named
spec
. It’s pretty similar to RSpec
.Let’s continue with the project we created in Chapter 04.
As you remember
crystal
created this project structure for us.$ cd sample && tree
-- LICENSE
-- README.md
-- shard.yml
-- spec
-- sample_spec.cr
-- spec_helper.cr
-- src
-- sample.cr
Did you see that
spec
folder? Yes, as you guess Crystal created this folder and the first spec for us. In Crystal a file is tested with corresponding _spec
file. Since we named our project as sample
it created a file named sample.cr
and the corresponding spec with spec/sample_spec.cr
.By the way, in this context
spec
and unit test
means the same so we can use them interchangeably.Without further ado lets open up
spec/sample_spec.cr
require "./spec_helper"
describe Sample do
# TODO: Write tests
it "works" do
false.should eq(true)
end
end
Now this file is pretty interesting. There a three important keywords,
describe
, it
and should
.Those keywords are only used in
spec
s with the following purposes.describe
lets you group related specs.it
is used for defining a spec with the given title in between “”.should
is used for making assumptions about the spec.
As you can see this file has a group
describe
d as Sample
and it
has one spec with the title of works
which makes the assumption that false should
equal true.You might be asking ‘How do we run these tests?’. Well
crystal
command to the rescue.$ KEMAL_ENV=test crystal spec
F
Failures:
1) Sample works
Failure/Error: false.should eq(true)
Expected: true
got: false
# spec/sample_spec.cr:7
Finished in 420 microseconds
1 examples, 1 failures, 0 errors, 0 pending
Failed examples:
crystal spec spec/sample_spec.cr:6 # Sample works
Yay! We got a failing(red) test. Reading the output we can easily find which spec failed. Here it’s the spec within the group of
Sample
titled works
a.k.a Sample works
. Let’s make it pass(green).require "./spec_helper"
describe Sample do
# TODO: Write tests
it "works" do
true.should eq(true)
end
end
Rerun the specs.
$ KEMAL_ENV=test crystal spec
.
Finished in 383 microseconds
1 examples, 0 failures, 0 errors, 0 pending
Green! That’s all you need to know to get started. Next up: FizzBuzz.
Last modified 5mo ago