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module RSpec
module Matchers
class Change
def initialize(receiver=nil, message=nil, &block)
@message = message
@value_proc = block || lambda {receiver.__send__(message)}
@expected_after = @expected_before = @minimum = @maximum = @expected_delta = nil
@eval_before = @eval_after = false
end
def matches?(event_proc)
raise_block_syntax_error if block_given?
@actual_before = evaluate_value_proc
event_proc.call
@actual_after = evaluate_value_proc
(!change_expected? || changed?) && matches_before? && matches_after? && matches_expected_delta? && 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
case val = @value_proc.call
when Array, Hash
val.dup
else
val
end
end
def failure_message_for_should
if @eval_before && !expected_matches_actual?(@expected_before, @actual_before)
"#{message} should have initially been #{@expected_before.inspect}, but was #{@actual_before.inspect}"
elsif @eval_after && !expected_matches_actual?(@expected_after, @actual_after)
"#{message} should have been changed to #{@expected_after.inspect}, but is now #{@actual_after.inspect}"
elsif @expected_delta
"#{message} should have been changed by #{@expected_delta.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 #{@actual_before.inspect}"
end
end
def actual_delta
@actual_after - @actual_before
end
def failure_message_for_should_not
"#{message} should not have changed, but did change from #{@actual_before.inspect} to #{@actual_after.inspect}"
end
def by(expected_delta)
@expected_delta = expected_delta
self
end
def by_at_least(minimum)
@minimum = minimum
self
end
def by_at_most(maximum)
@maximum = maximum
self
end
def to(to)
@eval_after = true
@expected_after = to
self
end
def from (before)
@eval_before = true
@expected_before = before
self
end
def description
"change ##{message}"
end
private
def message
@message || "result"
end
def change_expected?
@expected_delta != 0
end
def changed?
@actual_before != @actual_after
end
def matches_before?
@eval_before ? expected_matches_actual?(@expected_before, @actual_before) : true
end
def matches_after?
@eval_after ? expected_matches_actual?(@expected_after, @actual_after) : true
end
def matches_expected_delta?
@expected_delta ? (@actual_before + @expected_delta == @actual_after) : true
end
def matches_min?
@minimum ? (@actual_after - @actual_before >= @minimum) : true
end
def matches_max?
@maximum ? (@actual_after - @actual_before <= @maximum) : true
end
def expected_matches_actual?(expected, actual)
expected === actual
end
end
# Applied to a proc, specifies that its execution will cause some value to
# change.
#
# @param [Object] receiver
# @param [Symbol] message the message to send the receiver
#
# You can either pass <tt>receiver</tt> and <tt>message</tt>, or a block,
# but not both.
#
# When passing a block, it must use the <tt>{ ... }</tt> format, not
# do/end, as <tt>{ ... }</tt> binds to the +change+ method, whereas do/end
# would errantly bind to the +should+ or +should_not+ method.
#
# == 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")
#
# lambda {
# doctor.leave_office
# }.should change(doctor, :sign).from(/is in/).to(/is out/)
#
# user = User.new(:type => "admin")
# lambda {
# user.symbolize_type
# }.should change(user, :type).from(String).to(Symbol)
#
# == Notes
#
# Evaluates <tt>receiver.message</tt> or <tt>block</tt> before and after it
# evaluates the proc object (generated by the lambdas in the examples
# above).
#
# <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>.
def change(receiver=nil, message=nil, &block)
Matchers::Change.new(receiver, message, &block)
end
end
end
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