gistfile1.txt

[1] pry(main)> class Foo; end
=> nil
[2] pry(main)> Foo.foo
NoMethodError: undefined method `foo' for Foo:Class
from (pry):3:in `<main>'
[3] pry(main)> class Foo; def self.foo; puts "foo"; end; end
=> nil
[4] pry(main)> Foo.foo
foo
=> nil
[5] pry(main)> Foo.bar
NoMethodError: undefined method `bar' for Foo:Class
from (pry):6:in `<main>'