Add expect to example_methods

- expect { this_block }.to change{this}.from(this).to(that)
- expect { this_block }.to raise_error

History.rdoc

@@ -4,6 +4,8 @@
 
   * name argument to mock/stub is now optional (closes #782)
     * you can do mock(:foo => "woo", :bar => "car")
+  * expect { this_block }.to change(this).from(this).to(that)
+  * expect { this_block }.to raise_error
 
 * bug fixes
 

features/expectations/expect_change.feature

@@ -0,0 +1,65 @@
+Feature: expect change
+
+  Expect some code (wrapped in a proc) to change the state of some object.
+
+  Scenario: expecting change
+    Given a file named "expect_change.rb" with:
+      """
+      class Counter
+        class << self
+          def increment
+            @count ||= 0
+            @count += 1
+          end
+          
+          def count
+            @count ||= 0
+          end
+        end
+      end
+      
+      describe Counter, "#increment" do
+        it "should increment the count" do
+          expect{Counter.increment}.to change{Counter.count}.from(0).to(1)
+        end
+
+        # deliberate failure
+        it "should increment the count by 2" do
+          expect{Counter.increment}.to change{Counter.count}.by(2)
+        end
+      end
+      """
+    When I run "spec expect_change.rb"
+    Then the stdout should match "2 examples, 1 failure"
+    Then the stdout should match "should have been changed by 2, but was changed by 1"
+
+  Scenario: expecting no change
+    Given a file named "expect_no_change.rb" with:
+      """
+      class Counter
+        class << self
+          def increment
+            @count ||= 0
+            @count += 1
+          end
+          
+          def count
+            @count ||= 0
+          end
+        end
+      end
+
+      describe Counter, "#increment" do
+        it "should not increment the count by 2" do
+          expect{Counter.increment}.to_not change{Counter.count}.from(0).to(2)
+        end
+
+        # deliberate failure
+        it "should not increment the count by 1" do
+          expect{Counter.increment}.to_not change{Counter.count}.by(1)
+        end
+      end
+      """
+    When I run "spec expect_no_change.rb"
+    Then the stdout should match "2 examples, 1 failure"
+    Then the stdout should match "should not have changed, but did change from 1 to 2"

features/expectations/expect_error.feature

@@ -0,0 +1,44 @@
+Feature: expect error
+
+  Expect a proc to change the state of some object.
+
+  Scenario: expect error
+    Given a file named "expect_error.rb" with:
+      """
+      describe Object, "#non_existent_message" do
+        it "should raise" do
+          expect{Object.non_existent_message}.to raise_error(NameError)
+        end
+      end
+
+      #deliberate failure
+      describe Object, "#public_instance_methods" do
+        it "should raise" do
+          expect{Object.public_instance_methods}.to raise_error(NameError)
+        end
+      end
+      """
+    When I run "spec expect_error.rb"
+    Then the stdout should match "2 examples, 1 failure"
+    Then the stdout should match "expected NameError but nothing was raised"
+
+  Scenario: expect no error
+    Given a file named "expect_no_error.rb" with:
+      """
+      describe Object, "#public_instance_methods" do
+        it "should not raise" do
+          expect{Object.public_instance_methods}.to_not raise_error(NameError)
+        end
+      end
+
+      #deliberate failure
+      describe Object, "#non_existent_message" do
+        it "should not raise" do
+          expect{Object.non_existent_message}.to_not raise_error(NameError)
+        end
+      end
+      """
+    When I run "spec expect_no_error.rb"
+    Then the stdout should match "2 examples, 1 failure"
+    Then the stdout should match "undefined method `non_existent_message'"
+

lib/spec/example/example_methods.rb

@@ -52,6 +52,15 @@ def execute(run_options, instance_variables) # :nodoc:
         run_options.reporter.example_finished(@_proxy.update(description), execution_error)
         success = execution_error.nil? || ExamplePendingError === execution_error
       end
+
+      module Aliases
+        alias_method :to,     :should
+        alias_method :to_not, :should_not
+      end
+
+      def expect(&block)
+        block.extend Aliases
+      end
 
       def eval_each_fail_fast(blocks) # :nodoc:
         blocks.each {|block| instance_eval(&block)}

spec/spec/example/example_methods_spec.rb

@@ -117,6 +117,18 @@ def module_that_is_reopened_method; end
         end.should raise_error(/No description supplied for example declared on this backtrace/)
       end
     end
+
+    describe "#expect" do
+      it "aliases #should with #to on the proc" do
+        a = 3
+        expect { a += 1 }.to change{a}.from(3).to(4)
+      end
+
+      it "aliases #should_not with #to_not on the proc" do
+        a = 3
+        expect { nil }.to_not change{a}
+      end
+    end
 
   end
 end