# spec/ruby

ruby/spec (https://github.com/ruby/spec/) is
a test suite for the Ruby language.

Once a month, @eregon merges the in-tree copy under spec/ruby
with the upstream repository, preserving the commits and history.
The same happens for other implementations such as JRuby and TruffleRuby.

Feel welcome to modify the in-tree spec/ruby.
This is the purpose of the in-tree copy,
to facilitate contributions to ruby/spec for MRI developers.

New features, additional tests for existing features and
regressions tests are all welcome in ruby/spec.
There is very little behavior that is implementation-specific,
as in the end user programs tend to rely on every behavior MRI exhibits.
In other words: If adding a spec might reveal a bug in
another implementation, then it is worth adding it.
Currently, the only module which is MRI-specific is `RubyVM`.

## Running ruby/spec

To run all specs:
```bash
make test-spec
```

Extra arguments can be added via `MSPECOPT`.
For instance, to show the help:
```bash
make test-spec MSPECOPT=-h
```

You can also run the specs in parallel, which is currently experimental.
It takes around 10s instead of 60s on a quad-core laptop.
```bash
make test-spec MSPECOPT=-j
```

To run a specific test, add its path to the command:
```bash
make test-spec MSPECOPT=spec/ruby/language/for_spec.rb
```

If ruby trunk is your current `ruby` in `$PATH`, you can also run `mspec` directly:
```bash
# change ruby to trunk
ruby -v # => trunk
spec/mspec/bin/mspec spec/ruby/language/for_spec.rb
```

## ruby/spec and test/

The main difference between a "spec" under spec/ruby and
a test under test/ is that specs are documenting what they test.
This is extremely valuable when reading these tests, as it
helps to quickly understand what specific behavior is tested,
and how a method should behave. Basic English is fine for spec descriptions.
Specs also tend to have few expectations (assertions) per spec,
as they specify one aspect of the behavior and not everything at once.
Beyond that, the syntax is slightly different but it does the same thing:
`assert_equal 3, 1+2` is just `(1+2).should == 3`.

Example:

```ruby
describe "The for expression" do
  it "iterates over an Enumerable passing each element to the block" do
    j = 0
    for i in 1..3
      j += i
    end
    j.should == 6
  end
end
```

For more details, see spec/ruby/CONTRIBUTING.md.
