Doing TDD
I facing a problem creating a book and assigning two authors with it. There is a failure in the creation. It says that there is an AssociationTypeMismatch: Author(#15100) expected, got nil which is an instance of NilClass(#40. I suppose that the format "authors: []" is not have been read well by something.
This is the test:
def test_has_many_and_belongs_to_mapping
apress = Publisher.find_by(name: 'Apress')
assert_equal 2, apress.books.size
book = Book.new(
title: 'Rails E-Commerce 3nd Edition',
authors: [
Author.find_by(first_name: 'Christian', last_name: 'Hellsten'),
Author.find_by(first_name: 'Jarkko', last_name: 'Laine')
],
published_at: Time.now,
isbn: '123-123-123-x',
blurb: 'E-Commerce on Rails',
page_count: 300,
price: 30.5
)
# apress.books << book
# apress.reload
# book.reload
# assert_equal 3, apress.books.size
# assert_equal 'Apress', book.publisher.name
end
This is the error:
MY ERD:
My schema:
CodePudding user response:
I think what you are missing is a meaningful setup
of data needed before this test runs. Even though those publishers and books may exist in your development environment/database, the test suite usually is configured to wipe the database clean between runs.
If you have fixtures defined, then you can reference them like this:
test/fixtures/publishers.yml
apress:
id: 1
name: Apress
test/fixtures/authors.yml
hellsten:
id: 1
first_name: Christian
last_name: Hellsten
laine:
id: 2
first_name: Jarkko
last_name: Laine
test/fixtures/books.yml
beginning_ruby:
title: Beginning Ruby
publisher_id: 1
ruby_recipes:
title: Ruby Recipes
publisher_id: 1
So that the test would look more like this:
def test_has_many_and_belongs_to_mapping
apress = publishers(:apress)
assert_equal 2, apress.books.size
book = Book.new(
title: 'Rails E-Commerce 3nd Edition',
authors: [
Author.find_by(first_name: 'Christian', last_name: 'Hellsten'),
Author.find_by(first_name: 'Jarkko', last_name: 'Laine')
],
published_at: Time.now,
isbn: '123-123-123-x',
blurb: 'E-Commerce on Rails',
page_count: 300,
price: 30.5
)
apress.books << book
apress.reload
book.reload
assert_equal 3, apress.books.size
assert_equal 'Apress', book.publisher.name
end
Or instead of using fixtures, you could create the content before the test:
So that the test would look more like this:
setup do
publisher = Publisher.create!(name: 'Apress')
publisher.books.create!(title: 'Beginning Ruby')
publisher.books.create!(title: 'Ruby Recipes')
Author.create!(first_name: 'Christian', last_name: 'Hellsten')
Author.create!(first_name: 'Jarkko', last_name: 'Laine')
end
def test_has_many_and_belongs_to_mapping
apress = Publisher.find_by(name: 'Apress')
assert_equal 2, apress.books.size
book = Book.new(
title: 'Rails E-Commerce 3nd Edition',
authors: [
Author.find_by(first_name: 'Christian', last_name: 'Hellsten'),
Author.find_by(first_name: 'Jarkko', last_name: 'Laine')
],
published_at: Time.now,
isbn: '123-123-123-x',
blurb: 'E-Commerce on Rails',
page_count: 300,
price: 30.5
)
apress.books << book
apress.reload
book.reload
assert_equal 3, apress.books.size
assert_equal 'Apress', book.publisher.name
end
That way your database has those values, and your find_by()
calls should return data, and not nil
.