Testing a Book Inventory Management System - Unit Testing Validations

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You want to be absolutely sure that the validations are working. One way of doing this is to create a unit test that tests that all fields are validated correctly.

Scaffolding already created a unit test for you, but it contains only a dummy test, so replace the code intest/unit/book_test.rbwith the following code:

require File.dirname(__FILE__) + '/../test_helper'

class BookTest < Test::Unit::TestCase
def test_failing_create
book = Book.new
assert_equal false, book.save

assert_equal 7, book.errors.size
assert book.errors.on(:title)
assert book.errors.on(:publisher)
assert book.errors.on(:authors)
assert book.errors.on(:published_at)
assert book.errors.on(:isbn)
assert book.errors.on(:page_count)
assert book.errors.on(:price)
end
end

The unit test creates a new book without specifying any values for any of the validated fields, such as the price. It then tries to save the book to the database. This triggers a validation of each of the fields to which you added validations. When you run the test, there is a validation failure on each of the fields—eight in total. We test for this condition with theassert_equalmethod. We also check that validations are done on the correct fields, by callingbook.errors.onon each validated field. This method returns the actual error message for the specified field, and if it returns nil, we know the validation is not working.

Run the unit test, and you should see it pass without errors:

$ ruby test/unit/book_test.rb

--------------------------------------------
Loaded suite test/unit/book_test
Started
.
Finished in 0.172 seconds.

1 tests, 9 assertions, 0 failures, 0 errors
--------------------------------------------

You should also test that a valid book can be saved to the database, by adding thetest_createmethod to the unit test, as follows:

fixtures :authors, :publishers

def test_create
book = Book.new(
:title => 'Ruby for Toddlers',
:publisher_id => Publisher.find(1).id,
:published_at => Time.now,
:authors => Author.find(:all),
:isbn => '123-123-123-1',
:blurb => 'The best book since "Bodo Bär zu Hause"',
:page_count => 12,
:price => 40.4
)

assert book.save
end

This test looks up an author and a publisher from the database. These are inserted by the publisher and author fixtures, which have also been added. The test creates a new book with valid parameters, including a publisher and author, and then validates that the book was saved successfully. Recall that callingsaveon the book object returnstrueif there are no validation errors.

Please check back next week for the continuation of this series.

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