1module Spec
2 module Matchers
3
4 #Based on patch from Wilson Bilkovich
5 class Change #:nodoc:
6 def initialize(receiver=nil, message=nil, &block)
7 @receiver = receiver
8 @message = message
9 @block = block
10 end
11
12 def matches?(target, &block)
13 if block
14 raise MatcherError.new(<<-EOF
15block passed to should or should_not change must use {} instead of do/end
16EOF
17)
18 end
19 @target = target
20 execute_change
21 return false if @from && (@from != @before)
22 return false if @to && (@to != @after)
23 return (@before + @amount == @after) if @amount
24 return ((@after - @before) >= @minimum) if @minimum
25 return ((@after - @before) <= @maximum) if @maximum
26 return @before != @after
27 end
28
29 def execute_change
30 @before = @block.nil? ? @receiver.send(@message) : @block.call
31 @target.call
32 @after = @block.nil? ? @receiver.send(@message) : @block.call
33 end
34
35 def failure_message
36 if @to
37 "#{result} should have been changed to #{@to.inspect}, but is now #{@after.inspect}"
38 elsif @from
39 "#{result} should have initially been #{@from.inspect}, but was #{@before.inspect}"
40 elsif @amount
41 "#{result} should have been changed by #{@amount.inspect}, but was changed by #{actual_delta.inspect}"
42 elsif @minimum
43 "#{result} should have been changed by at least #{@minimum.inspect}, but was changed by #{actual_delta.inspect}"
44 elsif @maximum
45 "#{result} should have been changed by at most #{@maximum.inspect}, but was changed by #{actual_delta.inspect}"
46 else
47 "#{result} should have changed, but is still #{@before.inspect}"
48 end
49 end
50
51 def result
52 @message || "result"
53 end
54
55 def actual_delta
56 @after - @before
57 end
58
59 def negative_failure_message
60 "#{result} should not have changed, but did change from #{@before.inspect} to #{@after.inspect}"
61 end
62
63 def by(amount)
64 @amount = amount
65 self
66 end
67
68 def by_at_least(minimum)
69 @minimum = minimum
70 self
71 end
72
73 def by_at_most(maximum)
74 @maximum = maximum
75 self
76 end
77
78 def to(to)
79 @to = to
80 self
81 end
82
83 def from (from)
84 @from = from
85 self
86 end
87 end
88
89 # :call-seq:
90 # should change(receiver, message, &block)
91 # should change(receiver, message, &block).by(value)
92 # should change(receiver, message, &block).from(old).to(new)
93 # should_not change(receiver, message, &block)
94 #
95 # Allows you to specify that a Proc will cause some value to change.
96 #
97 # == Examples
98 #
99 # lambda {
100 # team.add_player(player)
101 # }.should change(roster, :count)
102 #
103 # lambda {
104 # team.add_player(player)
105 # }.should change(roster, :count).by(1)
106 #
107 # lambda {
108 # team.add_player(player)
109 # }.should change(roster, :count).by_at_least(1)
110 #
111 # lambda {
112 # team.add_player(player)
113 # }.should change(roster, :count).by_at_most(1)
114 #
115 # string = "string"
116 # lambda {
117 # string.reverse
118 # }.should change { string }.from("string").to("gnirts")
119 #
120 # lambda {
121 # person.happy_birthday
122 # }.should change(person, :birthday).from(32).to(33)
123 #
124 # lambda {
125 # employee.develop_great_new_social_networking_app
126 # }.should change(employee, :title).from("Mail Clerk").to("CEO")
127 #
128 # Evaluates +receiver.message+ or +block+ before and
129 # after it evaluates the c object (generated by the lambdas in the examples above).
130 #
131 # Then compares the values before and after the +receiver.message+ and
132 # evaluates the difference compared to the expected difference.
133 #
134 # == Warning
135 # +should_not+ +change+ only supports the form with no subsequent calls to
136 # +by+, +by_at_least+, +by_at_most+, +to+ or +from+.
137 #
138 # blocks passed to +should+ +change+ and +should_not+ +change+
139 # must use the <tt>{}</tt> form (<tt>do/end</tt> is not supported)
140 def change(target=nil, message=nil, &block)
141 Matchers::Change.new(target, message, &block)
142 end
143 end
144end