# 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`

```ruby
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.

```ruby
$ 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).

```ruby
require "./spec_helper"

describe Sample do
  # TODO: Write tests

  it "works" do
    true.should eq(true)
  end
end
```

Rerun the specs.

```ruby
$ 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.


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