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module RSpec
module Matchers
#Based on patch from Wilson Bilkovich
class Change #:nodoc:
def initialize(receiver=nil, message=nil, &block)
@message = message
@value_proc = block || lambda {receiver.__send__(message)}
@to = @from = @minimum = @maximum = @amount = nil
@given_from = @given_to = false
end
def matches?(event_proc)
raise_block_syntax_error if block_given?
@before = evaluate_value_proc
event_proc.call
@after = evaluate_value_proc
(!change_expected? || changed?) && matches_before? && matches_after? && matches_amount? && matches_min? && matches_max?
end
def raise_block_syntax_error
raise MatcherError.new(<<-MESSAGE
block passed to should or should_not change must use {} instead of do/end
MESSAGE
)
end
def evaluate_value_proc
@value_proc.call
end
def failure_message_for_should
if @given_from && @before != @from
"#{message} should have initially been #{@from.inspect}, but was #{@before.inspect}"
elsif @given_to && @to != @after
"#{message} should have been changed to #{@to.inspect}, but is now #{@after.inspect}"
elsif @amount
"#{message} should have been changed by #{@amount.inspect}, but was changed by #{actual_delta.inspect}"
elsif @minimum
"#{message} should have been changed by at least #{@minimum.inspect}, but was changed by #{actual_delta.inspect}"
elsif @maximum
"#{message} should have been changed by at most #{@maximum.inspect}, but was changed by #{actual_delta.inspect}"
else
"#{message} should have changed, but is still #{@before.inspect}"
end
end
def actual_delta
@after - @before
end
def failure_message_for_should_not
"#{message} should not have changed, but did change from #{@before.inspect} to #{@after.inspect}"
end
def by(amount)
@amount = amount
self
end
def by_at_least(minimum)
@minimum = minimum
self
end
def by_at_most(maximum)
@maximum = maximum
self
end
def to(to)
@given_to = true
@to = to
self
end
def from (from)
@given_from = true
@from = from
self
end
def description
"change ##{message}"
end
private
def message
@message || "result"
end
def change_expected?
@amount != 0
end
def changed?
@before != @after
end
def matches_before?
@given_from ? @from == @before : true
end
def matches_after?
@given_to ? @to == @after : true
end
def matches_amount?
@amount ? (@before + @amount == @after) : true
end
def matches_min?
@minimum ? (@after - @before >= @minimum) : true
end
def matches_max?
@maximum ? (@after - @before <= @maximum) : true
end
end
# :call-seq:
# should change(receiver, message, &block)
# should change(receiver, message, &block).by(value)
# should change(receiver, message, &block).from(old).to(new)
# should_not change(receiver, message, &block)
#
# Allows you to specify that a Proc will cause some value to change.
#
# You can either pass <tt>receiver</tt> and <tt>message</tt>, or a block,
# but not both.
#
# == Examples
#
# lambda {
# team.add_player(player)
# }.should change(roster, :count)
#
# lambda {
# team.add_player(player)
# }.should change(roster, :count).by(1)
#
# lambda {
# team.add_player(player)
# }.should change(roster, :count).by_at_least(1)
#
# lambda {
# team.add_player(player)
# }.should change(roster, :count).by_at_most(1)
#
# string = "string"
# lambda {
# string.reverse!
# }.should change { string }.from("string").to("gnirts")
#
# lambda {
# person.happy_birthday
# }.should change(person, :birthday).from(32).to(33)
#
# lambda {
# employee.develop_great_new_social_networking_app
# }.should change(employee, :title).from("Mail Clerk").to("CEO")
#
# Evaluates <tt>receiver.message</tt> or <tt>block</tt> before and after
# it evaluates the c object (generated by the lambdas in the examples
# above).
#
# Then compares the values before and after the <tt>receiver.message</tt>
# and evaluates the difference compared to the expected difference.
#
# == WARNING
# <tt>should_not change</tt> only supports the form with no
# subsequent calls to <tt>by</tt>, <tt>by_at_least</tt>,
# <tt>by_at_most</tt>, <tt>to</tt> or <tt>from</tt>.
#
# blocks passed to <tt>should</tt> <tt>change</tt> and <tt>should_not</tt>
# <tt>change</tt> must use the <tt>{}</tt> form (<tt>do/end</tt> is not
# supported).
#
def change(receiver=nil, message=nil, &block)
Matchers::Change.new(receiver, message, &block)
end
end
end
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