unable to locate element in Ruby simple script fail - ruby

Question

When I run the script:
require 'rubygems'
require 'watir-webdriver'
#browser = Watir::Browser.new :firefox
def adopt_puppy_number(num)
#browser.button(:value => 'View details', :index => num - 1).click
#browser.button(:value => 'Adopt Me!').click
end
#browser.goto 'http://puppies.herokuapp.com'
adopt_puppy_number 1
#browser.button(:value => 'Adopt Another Puppy').click
adopt_puppy_number 2
I get the exception:
/var/lib/gems/1.9.1/gems/watir-webdriver-0.9.1/lib/watir-webdriver/elements/element.rb:536:in `assert_element_found': unable to locate element, using {:value=>"View details", :index=>0, :tag_name=>"button"} (Watir::Exception::UnknownObjectException)
from /var/lib/gems/1.9.1/gems/watir-webdriver-0.9.1/lib/watir-webdriver/elements/element.rb:508:in `assert_exists'
from /var/lib/gems/1.9.1/gems/watir-webdriver-0.9.1/lib/watir-webdriver/elements/element.rb:114:in `click'
from /home/giz/Downloads/RubymineProjects/learn_watir/thirdscript_dry.rb:6:in `adopt_puppy_number'
from /home/giz/Downloads/RubymineProjects/learn_watir/thirdscript_dry.rb:11:in `<top (required)>'
from -e:1:in `load'
from -e:1:in `<main>'
Why? Maybe I should add a wait command, but where exactly and which one?

Answer 1

The HTML for the View Details button is:
<input class="rounded_button" value="View Details" type="submit">
Notice that the value attribute is "View Details" not "View details". Watir's locators are case-sensitive, which is the element is not found. The adopt_puppy_number method should be:
def adopt_puppy_number(num)
#browser.button(:value => 'View Details', :index => num - 1).click
#browser.button(:value => 'Adopt Me!').click
end