What's the best way to unit test protected & private methods in Ruby?

Question

What\'s the best way to unit test protected and private methods in Ruby, using the standard Ruby Test::Unit framework?

I\'m sure somebody will pipe up a

Answer 1

Here's one easy way if you use RSpec:

before(:each) do
  MyClass.send(:public, *MyClass.protected_instance_methods)  
end

Answer 2

You can "reopen" the class and provide a new method that delegates to the private one:

class Foo
  private
  def bar; puts "Oi! how did you reach me??"; end
end
# and then
class Foo
  def ah_hah; bar; end
end
# then
Foo.new.ah_hah

Answer 3

In Test::Unit framework can write,

MyClass.send(:public, :method_name)

Here "method_name" is private method.

& while calling this method can write,

assert_equal expected, MyClass.instance.method_name(params)

Answer 4

Instead of obj.send you can use a singleton method. It’s 3 more lines of code in your test class and requires no changes in the actual code to be tested.

def obj.my_private_method_publicly (*args)
  my_private_method(*args)
end

In the test cases you then use my_private_method_publicly whenever you want to test my_private_method.

http://mathandprogramming.blogspot.com/2010/01/ruby-testing-private-methods.html

obj.send for private methods was replaced by send! in 1.9, but later send! was removed again. So obj.send works perfectly well.

Answer 5

Just reopen the class in your test file, and redefine the method or methods as public. You don't have to redefine the guts of the method itself, just pass the symbol into the public call.

If you original class is defined like this:

class MyClass

  private

  def foo
    true
  end
end

In you test file, just do something like this:

class MyClass
  public :foo

end

You can pass multiple symbols to public if you want to expose more private methods.

public :foo, :bar

Answer 6

I know I'm late to the party, but don't test private methods....I can't think of a reason to do this. A publicly accessible method is using that private method somewhere, test the public method and the variety of scenarios that would cause that private method to be used. Something goes in, something comes out. Testing private methods is a big no-no, and it makes it much harder to refactor your code later. They are private for a reason.