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Update docs for #allow_value

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* Remove explanation of and de-emphasize difference between `should
  allow_value` and `should_not allow_value`; reword.
* Add docs for `ignoring_inteference_by_writer` and background on when
  one would get a CouldNotSetAttributeError.

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Elliot Winkler 2015-09-30 12:51:01 -06:00
parent 965ca7e126
commit 0fbd4bff27
2 changed files with 145 additions and 30 deletions
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3
README.md
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@ -16,7 +16,8 @@ interested in the README for 2.8.0 instead.][2.8.0-README]**
* **[allow_mass_assignment_of](lib/shoulda/matchers/active_model/allow_mass_assignment_of_matcher.rb)**
tests usage of Rails 3's `attr_accessible` and `attr_protected` macros.
* **[allow_value](lib/shoulda/matchers/active_model/allow_value_matcher.rb)**
tests usage of the `validates_format_of` validation.
tests that an attribute is valid or invalid if set to one or more values.
*(Aliased as #allow_values.)*
* **[have_secure_password](lib/shoulda/matchers/active_model/have_secure_password_matcher.rb)**
tests usage of `has_secure_password`.
* **[validate_absence_of](lib/shoulda/matchers/active_model/validate_absence_of_matcher.rb)**

172
lib/shoulda/matchers/active_model/allow_value_matcher.rb
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@ -1,15 +1,11 @@
module Shoulda
module Matchers
module ActiveModel
# The `allow_value` matcher is used to test that an attribute of a model
# can or cannot be set to a particular value or values. It is most
# commonly used in conjunction with the `validates_format_of` validation.
# The `allow_value` matcher (or its alias, `allow_values`) is used to
# ensure that an attribute is valid or invalid if set to one or more
# values.
#
# #### should
#
# In the positive form, `allow_value` asserts that an attribute can be
# set to one or more values, succeeding if none of the values cause the
# record to be invalid:
# Take this model for example:
#
# class UserProfile
# include ActiveModel::Model
@ -18,45 +14,136 @@ module Shoulda
# validates_format_of :website_url, with: URI.regexp
# end
#
# You can use `allow_value` to test one value at a time:
#
# # RSpec
# describe UserProfile do
# it { should allow_value('http://foo.com').for(:website_url) }
# it { should allow_value('http://bar.com').for(:website_url) }
# end
#
# # Test::Unit
# class UserProfileTest < ActiveSupport::TestCase
# should allow_value('http://foo.com').for(:website_url)
# should allow_value('http://bar.com').for(:website_url)
# end
#
# You can also test multiple values in one go, if you like. In the
# positive sense, this makes an assertion that none of the values cause the
# record to be invalid. In the negative sense, this makes an assertion
# that none of the values cause the record to be valid:
#
# # RSpec
# describe UserProfile do
# it do
# should allow_value('http://foo.com', 'http://bar.com/baz').
# should allow_values('http://foo.com', 'http://bar.com').
# for(:website_url)
# end
#
# it do
# should_not allow_values('http://foo.com', 'buz').
# for(:website_url)
# end
# end
#
# # Test::Unit
# class UserProfileTest < ActiveSupport::TestCase
# should allow_value('http://foo.com', 'http://bar.com/baz').
# should allow_values('http://foo.com', 'http://bar.com/baz').
# for(:website_url)
#
# should_not allow_values('http://foo.com', 'buz').
# for(:website_url)
# end
#
# #### should_not
# #### Caveats
#
# In the negative form, `allow_value` asserts that an attribute cannot be
# set to one or more values, succeeding if the *first* value causes the
# record to be invalid.
# When using `allow_value` or any matchers that depend on it, you may
# encounter a CouldNotSetAttributeError. This exception is raised if the
# matcher, in attempting to set a value on the attribute, detects that
# the value set is different from the value that the attribute returns
# upon reading it back.
#
# **This can be surprising** so in this case if you need to check that
# *all* of the values are invalid, use separate assertions:
# This usually happens if the writer method (`foo=`, `bar=`, etc.) for
# that attribute has custom logic to ignore certain incoming values or
# change them in any way. Here are three examples we've seen:
#
# class UserProfile
# include ActiveModel::Model
# attr_accessor :website_url
# * You're attempting to assert that an attribute should not allow nil,
# yet the attribute's writer method contains a conditional to do nothing
# if the attribute is set to nil:
#
# validates_format_of :website_url, with: URI.regexp
# end
# class Foo
# include ActiveModel::Model
#
# describe UserProfile do
# # One assertion: 'buz' and 'bar' will not be tested
# it { should_not allow_value('fiz', 'buz', 'bar').for(:website_url) }
# attr_reader :bar
#
# # Three assertions, all tested separately
# it { should_not allow_value('fiz').for(:website_url) }
# it { should_not allow_value('buz').for(:website_url) }
# it { should_not allow_value('bar').for(:website_url) }
# end
# def bar=(value)
# return if value.nil?
# @bar = value
# end
# end
#
# describe Foo do
# it do
# foo = Foo.new
# foo.bar = "baz"
# # This will raise a CouldNotSetAttributeError since `foo.bar` is now "123"
# expect(foo).not_to allow_value(nil).for(:bar)
# end
# end
#
# * You're attempting to assert that an numeric attribute should not allow a
# string that contains non-numeric characters, yet the writer method for
# that attribute strips out non-numeric characters:
#
# class Foo
# include ActiveModel::Model
#
# attr_reader :bar
#
# def bar=(value)
# @bar = value.gsub(/\D+/, '')
# end
# end
#
# describe Foo do
# it do
# foo = Foo.new
# # This will raise a CouldNotSetAttributeError since `foo.bar` is now "123"
# expect(foo).not_to allow_value("abc123").for(:bar)
# end
# end
#
# * You're passing a value to `allow_value` that the model typecasts into
# another value:
#
# describe Foo do
# # Assume that `attr` is a string
# # This will raise a CouldNotSetAttributeError since `attr` typecasts `[]` to `"[]"`
# it { should_not allow_value([]).for(:attr) }
# end
#
# So when you encounter this exception, you have a couple of options:
#
# * If you understand the problem and wish to override this behavior to
# get around this exception, you can add the
# `ignoring_interference_by_writer` qualifier like so:
#
# it do
# should_not allow_value([]).
# for(:attr).
# ignoring_interference_by_writer
# end
#
# * Note, however, that the above option will not always cause the test to
# pass. In this case, this is telling you that you don't need to use
# `allow_value`, or quite possibly even the validation that you're
# testing altogether. In any case, we would probably make the argument
# that since it's clear that something is responsible for sanitizing
# incoming data before it's stored in your model, there's no need to
# ensure that sanitization places the model in a valid state, if such
# sanitization creates valid data. In terms of testing, the sanitization
# code should probably be tested, but not the effects of that
# sanitization on the validness of the model.
#
# #### Qualifiers
#
@ -185,6 +272,32 @@ module Shoulda
# )
# end
#
# ##### ignoring_interference_by_writer
#
# Use `ignoring_interference_by_writer` if you've encountered a
# CouldNotSetAttributeError and wish to ignore it. Please read the Caveats
# section above for more information.
#
# class Address < ActiveRecord::Base
# # Address has a zip_code field which is a string
# end
#
# # RSpec
# describe Address do
# it do
# should_not allow_value([]).
# for(:zip_code).
# ignoring_interference_by_writer
# end
# end
#
# # Test::Unit
# class AddressTest < ActiveSupport::TestCase
# should_not allow_value([]).
# for(:zip_code).
# ignoring_interference_by_writer
# end
#
# @return [AllowValueMatcher]
#
def allow_value(*values)
@ -194,6 +307,7 @@ module Shoulda
AllowValueMatcher.new(*values)
end
end
# @private
alias_method :allow_values, :allow_value
# @private