Rails: How to test code in the lib/ directory?

I have a model which gets its data from a parser object. I'm thinking that the parser class should live in the lib/ directory (although I could be persuaded that it should live soewhere else). The question is: Where should my unit tests for the parser class be? And how do I ensure that they are run each time I run rake test?

In the Rails application I'm working on, I decided to just place the tests in the test\unit directory. I will also nest them by module/directory as well, for example:

lib/a.rb   => test/unit/a_test.rb
lib/b/c.rb => test/unit/b/c_test.rb

For me, this was the path of last resistance, as these tests ran without having to make any other changes.

Here's one way:

Create lib/tasks/test_lib_dir.rake with the following

namespace :test do
  
  desc "Test lib source"
  Rake::TestTask.new(:lib) do |t|    
    t.libs << "test"
    t.pattern = 'test/lib/**/*_test.rb'
    t.verbose = true    
  end
  
end

Mimic the structure of your lib dir under the test dir, replacing lib code with corresponding tests.

Run rake test:lib to run your lib tests.

If you want all tests to run when you invoke rake test, you could add the following to your new rake file.

lib_task = Rake::Task["test:lib"]
test_task = Rake::Task[:test]
test_task.enhance { lib_task.invoke }

I was looking to do the same thing but with rspec & autospec and it took a little digging to figure out just where they were getting the list of directories / file patterns that dictated which test files to run. Ultimately I found this in lib/tasks/rspec.rake:86

  [:models, :controllers, :views, :helpers, :lib, :integration].each do |sub|
    desc "Run the code examples in spec/#{sub}"
    Spec::Rake::SpecTask.new(sub => spec_prereq) do |t|
      t.spec_opts = ['--options', "\"#{RAILS_ROOT}/spec/spec.opts\""]
      t.spec_files = FileList["spec/#{sub}/**/*_spec.rb"]
    end
  end

I had placed my tests in a new spec/libs directory when the rpsec.rake file was configured to look in spec/lib. Simply renaming libs -> lib did the trick!

An easy and clean way is just to create a directory under test/unit/lib. Then create test as test/unit/lib/foo_test.rb corresponding to lib/foo.rb. No new rake tasks required, and you can nest more directories if needed to match the lib directory structure.

As of Rails 4.0:

rake test:all         # Run all tests in any subdir of `test` without resetting the DB
rake test:all:db      # Same as above and resets the DB

As of Rails 4.1, redefine test:run to include additional tasks when running rake or rake test:

# lib/tasks/test.rake

namespace :test do
  Rake::Task["run"].clear
  task run: ["test:units", "test:functionals", "test:generators", "test:integration", "test:tasks"]

  ["tasks"].each do |name|
    Rails::TestTask.new(name => "test:prepare") do |t|
      t.pattern = "test/#{name}/**/*_test.rb"
    end
  end
end

This has the added bonus of defining rake test:tasks in the given example.

As of Rails 4.2, test:run includes all subdirs of test including them when running rake test, and thus rake.

To not define additional rake tasks to run tests from the custom defined folders you may also run them with the command rake test:all. Tests folders structure for the lib folder or any other custom folder is up to you. But I prefer to duplicate them in classes: lib is matched to test/lib, app/form_objects to test/form_objects.

Use:

[spring] rake test:all

to run all tests, including the directories you created (like [root]/test/lib/).

Omit [spring] if tou aren't using it.