Add Rubocop check to avoid using `be_success`

Prevent using `be_success` call in controller specs to avoid
getting following deprecation warning:

```
DEPRECATION WARNING: The success? predicate is deprecated and
will be removed in Rails 6.0.
Please use successful? as provided by Rack::Response::Helpers.
```

1 files changed, 50 insertions, 0 deletions

diff --git a/rubocop/cop/rspec/be_success_matcher.rb b/rubocop/cop/rspec/be_success_matcher.rb
new file mode 100644
index 00000000000..a137e2dba69
--- /dev/null
+++ b/rubocop/cop/rspec/be_success_matcher.rb
@@ -0,0 +1,50 @@
+require_relative '../../spec_helpers'
+
+module RuboCop
+  module Cop
+    module RSpec
+      # This cop checks for `be_success` usage in controller specs
+      #
+      # @example
+      #
+      #   # bad
+      #   it "responds with success" do
+      #     expect(response).to be_success
+      #   end
+      #
+      #   it { is_expected.to be_success }
+      #
+      #   # good
+      #   it "responds with success" do
+      #     expect(response).to be_successful
+      #   end
+      #
+      #   it { is_expected.to be_successful }
+      #
+      class BeSuccessMatcher < RuboCop::Cop::Cop
+        include SpecHelpers
+
+        MESSAGE = "Don't use deprecated `success?` method, use `successful?` instead.".freeze
+
+        def_node_search :expect_to_be_success?, <<~PATTERN
+          (send (send nil? :expect (send nil? ...)) :to (send nil? :be_success))
+        PATTERN
+
+        def_node_search :is_expected_to_be_success?, <<~PATTERN
+          (send (send nil? :is_expected) :to (send nil? :be_success))
+        PATTERN
+
+        def be_success_usage?(node)
+          expect_to_be_success?(node) || is_expected_to_be_success?(node)
+        end
+
+        def on_send(node)
+          return unless in_controller_spec?(node)
+          return unless be_success_usage?(node)
+
+          add_offense(node, location: :expression, message: MESSAGE)
+        end
+      end
+    end
+  end
+end