Deprecate #refund helpers on Charge and ApplicationFee

As discussed previously in #354 and alluded to in #363, this patch
deprecates the `#refund` helpers on `Charge` and `ApplicationFee` in
favor of the resource-centric approach (i.e. `charge.refunds.create`).

We do this for a few reasons:

1. The new approach is far preferred and uses our modern endpoints. It's
   also been the mechanism suggested by the documentation for ages now.
2. The old approach is somewhat risky in that a forgotten "s" can lead
   to an accidental refund (i.e. `charge.refund` instead of
   `charge.refunds`).

Follows up #354. Fixes #363.

lib/stripe/application_fee.rb

@@ -16,5 +16,7 @@ module Stripe
       # from the server
       self.refresh
     end
+    extend Gem::Deprecate
+    deprecate :refund, "application_fee.refunds.create", 2016, 07
   end
 end

lib/stripe/charge.rb

@@ -8,6 +8,8 @@ module Stripe
       response, opts = request(:post, refund_url, params, opts)
       initialize_from(response, opts)
     end
+    extend Gem::Deprecate
+    deprecate :refund, "charge.refunds.create", 2016, 07
 
     def capture(params={}, opts={})
       response, opts = request(:post, capture_url, params, opts)

test/stripe/api_resource_test.rb

@@ -206,12 +206,12 @@ module Stripe
               opts[:headers][:authorization] == 'Bearer local'
           end.returns(make_response(make_charge))
           Stripe.expects(:execute_request).with do |opts|
-            opts[:url] == "#{Stripe.api_base}/v1/charges/ch_test_charge/refund" &&
+            opts[:url] == "#{Stripe.api_base}/v1/charges/ch_test_charge/refunds" &&
               opts[:headers][:authorization] == 'Bearer local'
-          end.returns(make_response(make_charge))
+          end.returns(make_response(make_refund))
 
           ch = Stripe::Charge.retrieve('ch_test_charge', 'local')
-          ch.refund
+          ch.refunds.create
         end
       end
     end

test/stripe/application_fee_test.rb

@@ -14,18 +14,37 @@ module Stripe
     should "application fees should be refundable" do
       fee = Stripe::ApplicationFee.construct_from(make_application_fee)
 
-      # first a post to create a refund
       @mock.expects(:post).once.
         with("#{Stripe.api_base}/v1/application_fees/#{fee.id}/refunds", nil, '').
         returns(make_response(make_application_fee_refund))
 
-      # then a get to refresh the current object
-      @mock.expects(:get).once.
-        with("#{Stripe.api_base}/v1/application_fees/#{fee.id}", nil, nil).
-        returns(make_response({:id => "fee_test_fee", :refunded => true}))
+      refund = fee.refunds.create
+      assert refund.is_a?(Stripe::ApplicationFeeRefund)
+    end
 
-      fee.refund
-      assert fee.refunded
+    should "warn that #refund is deprecated" do
+      old_stderr = $stderr
+      $stderr = StringIO.new
+      begin
+        fee = Stripe::ApplicationFee.construct_from(make_application_fee)
+
+        # creates the refund
+        @mock.expects(:post).once.
+          with("#{Stripe.api_base}/v1/application_fees/#{fee.id}/refunds", nil, '').
+          returns(make_response({}))
+
+        # reloads the application fee to get the field updates
+        @mock.expects(:get).once.
+          with("#{Stripe.api_base}/v1/application_fees/#{fee.id}", nil, nil).
+          returns(make_response({:id => fee.id, :refunded => true}))
+
+        fee.refund
+        message = "NOTE: Stripe::ApplicationFee#refund is deprecated; use " +
+          "application_fee.refunds.create instead"
+        assert_match Regexp.new(message), $stderr.string
+      ensure
+        $stderr = old_stderr
+      end
     end
   end
 end

test/stripe/charge_test.rb

@@ -12,11 +12,11 @@ module Stripe
     end
 
     should "charges should be refundable" do
+      c = Stripe::Charge.construct_from(make_charge)
       @mock.expects(:get).never
-      @mock.expects(:post).once.returns(make_response({:id => "ch_test_charge", :refunded => true}))
-      c = Stripe::Charge.new("test_charge")
-      c.refund
-      assert c.refunded
+      @mock.expects(:post).once.returns(make_response(make_refund(:charge => c)))
+      r = c.refunds.create
+      assert r.is_a?(Stripe::Refund)
     end
 
     should "charges should not be deletable" do
@@ -114,5 +114,22 @@ module Stripe
       })
       assert c.paid
     end
+
+    should "warn that #refund is deprecated" do
+      old_stderr = $stderr
+      $stderr = StringIO.new
+      begin
+        charge = Stripe::Charge.construct_from(make_charge)
+        @mock.expects(:post).once.
+          with("#{Stripe.api_base}/v1/charges/#{charge.id}/refund", nil, '').
+          returns(make_response({:id => charge.id, :refunded => true}))
+        charge.refund
+        message = "NOTE: Stripe::Charge#refund is deprecated; use " +
+          "charge.refunds.create instead"
+        assert_match Regexp.new(message), $stderr.string
+      ensure
+        $stderr = old_stderr
+      end
+    end
   end
 end