add argument_matchers features for explicit arguments, anything, any_…

…args, and no_args

features/argument_matchers/README.md

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+### Introduction
+
+Argument matchers can be used:
+
+* In stubs to constrain the scope of the stubbed method
+
+      obj.stub(:foo).with(:bar) do |arg|
+        #do something for :bar
+      end
+      obj.stub(:foo).with(:baz) do |arg|
+        #do something for :baz
+      end
+
+* In expectations to validate the arguments that should be received in a method call
+
+      #create a double
+      obj = double()
+      
+      #expect a message with given args
+      obj.should_receive(:message).with('an argument')
+
+If more control is needed, one can use a block
+
+    obj.should_receive(:message) do |arg1,  arg2|
+      # set expectations about the args in this block
+      # and optionally set a return value
+    end

features/argument_matchers/explicit.feature

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+Feature: explicit arguments
+
+  Allows you to explicitly specify the argument values
+
+  Scenario: explicit arguments
+    Given a file named "stub_explicit_args_spec.rb" with:
+      """
+      describe "stubbed explicit arguments" do
+        it "works on stubs" do
+          object = Object.new
+          object.stub(:foo).with(:this) do |arg|
+            "got this"
+          end
+          object.stub(:foo).with(:that) do |arg|
+            "got that"
+          end
+
+          object.foo(:this).should eq("got this")
+          object.foo(:that).should eq("got that")
+        end
+
+        it "works on doubles and expectations" do
+          object = double('foo')
+          object.should_receive(:bar).with(:foo)
+
+          object.bar(:foo)
+        end
+      end
+      """
+    When I run `rspec stub_explicit_args_spec.rb`
+    Then the output should contain "2 examples, 0 failures"
+
+  Scenario: explicit arguments with multiple arities
+    Given a file named "stub_multiple_explicit_args_spec.rb" with:
+      """
+      describe "stubbed multiple explicit arguments" do
+        it "works on stubs" do
+          object = Object.new
+          object.stub(:foo).with(:this) do |arg|
+            "got this"
+          end
+          object.stub(:foo).with(:this, :that) do |arg1, arg2|
+            "got this and that"
+          end
+
+          object.foo(:this).should eq("got this")
+          object.foo(:this, :that).should eq("got this and that")
+        end
+        
+        it "works on mocks" do
+          object = double('foo')
+          object.should_receive(:foo).with(:this, :that)
+
+          object.foo(:this, :that)
+        end
+      end
+      """
+    When I run `rspec stub_multiple_explicit_args_spec.rb`
+    Then the output should contain "2 examples, 0 failures"
+

features/argument_matchers/general_matchers.feature

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+Feature: General matchers
+
+  The `anything`,  `any_args`,  and `no_args` matchers can be used to require the method 
+  to have arguments (or not) without constraining the details of the argument, such as its
+  type,  pattern or value. The `anything` matcher only reflects a single argument, while
+  the `any_args` matcher matches any arity.
+
+  Scenario: anything argument matcher
+    Given a file named "stub_anything_args_spec.rb" with:
+      """
+      describe "stubbed anything() args spec" do
+        it "works" do
+          object = Object.new
+          object.stub(:foo).with(anything) do
+            "anything"
+          end
+
+          object.foo(1).should eq("anything")
+          object.foo(:that).should eq("anything")
+        end
+      end
+      """
+    When I run `rspec stub_anything_args_spec.rb`
+    Then the output should contain "1 example, 0 failures"
+
+  Scenario: any_args argument matcher
+    Given a file named "stub_any_args_spec.rb" with:
+      """
+      describe "stubbed any_args() args spec" do
+        it "works" do
+          object = Object.new
+          object.stub(:foo).with(any_args) do
+            "anything"
+          end
+
+          object.foo(1).should eq("anything")
+          object.foo(:that).should eq("anything")
+          object.foo.should eq("anything")
+        end
+      end
+      """
+    When I run `rspec stub_any_args_spec.rb`
+    Then the output should contain "1 example, 0 failures"
+
+  Scenario: no_args argument matcher
+    Given a file named "stub_no_args_spec.rb" with:
+      """
+      describe "stubbed no_args() args spec" do
+        it "works for no args" do
+          object = Object.new
+          object.stub(:foo).with(no_args) do
+            "nothing"
+          end
+          object.stub(:foo).with(anything) do
+            "something"
+          end
+
+          object.foo(:that).should eq("something")
+          object.foo.should eq("nothing")
+        end
+      end
+      """
+    When I run `rspec stub_no_args_spec.rb`
+    Then the output should contain "1 example, 0 failures"
+
+  Scenario: no_args argument matcher for expectations
+    Given a file named "stub_no_args_expectations_spec.rb" with:
+      """
+      describe "stubbed no_args() args spec for expectations" do
+        it "works for no args" do
+          object = Object.new
+          object.should_receive(:foo).with(no_args)
+
+          object.foo
+        end
+        it "fails for args" do
+          object = Object.new
+          object.should_receive(:foo).with(no_args)
+
+          object.foo(:bar)
+        end
+      end
+      """
+    When I run `rspec stub_no_args_expectations_spec.rb`
+    Then the output should contain "2 examples, 1 failure"

features/argument_matchers/type_matchers.feature

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+Feature: stub with argument constraints
+
+  You can further specify the behavior by constraining the type, format and/or number of arguments with the #with() method chained off of #stub()
+
+  Scenario: an_instance_of argument matcher
+    Given a file named "stub_an_instance_of_args_spec.rb" with:
+      """
+      describe "stubbed an_instance_of() args spec" do
+        it "works" do
+          object = Object.new
+          object.stub(:foo).with(an_instance_of(Symbol)) do
+            "symbol"
+          end
+          object.stub(:foo).with(an_instance_of(String)) do
+            "string"
+          end
+
+          object.foo("bar").should eq("string")
+          object.foo(:that).should eq("symbol")
+        end
+      end
+      """
+    When I run `rspec stub_an_instance_of_args_spec.rb`
+    Then the output should contain "1 example, 0 failures"
+