Check that stubs aren't added to mocks

config/default.yml

@@ -283,6 +283,11 @@ RSpec/MissingExampleGroupArgument:
   Enabled: true
   StyleGuide: http://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/MissingExampleGroupArgument
 
+RSpec/MockNotStub:
+  Description: Checks that stubs aren't added to mocks.
+  Enabled: true
+  StyleGuide: http://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/MockNotStub
+
 RSpec/MultipleDescribes:
   Description: Checks for multiple top level describes.
   Enabled: true

lib/rubocop/cop/rspec/mock_not_stub.rb

@@ -0,0 +1,73 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module RSpec
+      # Checks that stubs aren't added to mocks.
+      #
+      # @example
+      #
+      #   # bad
+      #   expect(foo).to receive(:bar).with(42).and_return("hello world")
+      #
+      #   # good (without spies)
+      #   allow(foo).to receive(:bar).with(42).and_return("hello world")
+      #   expect(foo).to receive(:bar).with(42)
+      #
+      #   # good (with spies)
+      #   allow(foo).to receive(:bar).with(42).and_return("hello world")
+      #   expect(foo).to have_received(:bar).with(42)
+      #
+      class MockNotStub < Cop
+        MSG = "Don't stub your mock.".freeze
+
+        def_node_matcher :message_expectation_with_return_argument, <<-PATTERN
+          (send
+            (send nil? :expect ...) :to
+            $(send #receive :and_return _)
+          )
+        PATTERN
+
+        def_node_matcher :message_expectation_with_return_block, <<-PATTERN
+          (send
+            (send nil? :expect ...) :to
+            $(block #receive (args) _)
+          )
+        PATTERN
+
+        def_node_matcher :receive, <<-PATTERN
+          {
+            (send nil? :receive ...)
+            (send (send nil? :receive ...) :with ...)
+          }
+        PATTERN
+
+        def on_send(node)
+          message_expectation_with_return_argument(node) do |match|
+            add_offense(match, location: offending_argument_range(match.loc))
+          end
+
+          message_expectation_with_return_block(node) do |match|
+            add_offense(match, location: offending_block_range(match.loc))
+          end
+        end
+
+        def offending_argument_range(source_map)
+          Parser::Source::Range.new(
+            source_map.expression.source_buffer,
+            source_map.dot.begin_pos,
+            source_map.end.end_pos
+          )
+        end
+
+        def offending_block_range(source_map)
+          Parser::Source::Range.new(
+            source_map.expression.source_buffer,
+            source_map.begin.begin_pos,
+            source_map.end.end_pos
+          )
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/rspec_cops.rb

@@ -52,6 +52,7 @@
 require_relative 'rspec/message_expectation'
 require_relative 'rspec/message_spies'
 require_relative 'rspec/missing_example_group_argument'
+require_relative 'rspec/mock_not_stub'
 require_relative 'rspec/multiple_describes'
 require_relative 'rspec/multiple_expectations'
 require_relative 'rspec/multiple_subjects'

manual/cops.md

@@ -53,6 +53,7 @@
 * [RSpec/MessageExpectation](cops_rspec.md#rspecmessageexpectation)
 * [RSpec/MessageSpies](cops_rspec.md#rspecmessagespies)
 * [RSpec/MissingExampleGroupArgument](cops_rspec.md#rspecmissingexamplegroupargument)
+* [RSpec/MockNotStub](cops_rspec.md#rspecmocknotstub)
 * [RSpec/MultipleDescribes](cops_rspec.md#rspecmultipledescribes)
 * [RSpec/MultipleExpectations](cops_rspec.md#rspecmultipleexpectations)
 * [RSpec/MultipleSubjects](cops_rspec.md#rspecmultiplesubjects)

manual/cops_rspec.md

@@ -1633,6 +1633,33 @@ end
 
 * [http://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/MissingExampleGroupArgument](http://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/MissingExampleGroupArgument)
 
+## RSpec/MockNotStub
+
+Enabled by default | Supports autocorrection
+--- | ---
+Enabled | No
+
+Checks that stubs aren't added to mocks.
+
+### Examples
+
+```ruby
+# bad
+expect(foo).to receive(:bar).with(42).and_return("hello world")
+
+# good (without spies)
+allow(foo).to receive(:bar).with(42).and_return("hello world")
+expect(foo).to receive(:bar).with(42)
+
+# good (with spies)
+allow(foo).to receive(:bar).with(42).and_return("hello world")
+expect(foo).to have_received(:bar).with(42)
+```
+
+### References
+
+* [http://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/MockNotStub](http://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/MockNotStub)
+
 ## RSpec/MultipleDescribes
 
 Enabled by default | Supports autocorrection

spec/rubocop/cop/rspec/mock_not_stub_spec.rb

@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::RSpec::MockNotStub do
+  subject(:cop) { described_class.new }
+
+  it 'flags expect(...).to receive(...).with(...).and_return' do
+    expect_offense(<<-RUBY)
+      expect(foo).to receive(:bar).with(42).and_return("hello world")
+                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^ Don't stub your mock.
+    RUBY
+  end
+
+  it 'flags expect(...).to receive(...).with(...) { } ' do
+    expect_offense(<<-RUBY)
+      expect(foo).to receive(:bar).with(42) { "hello world" }
+                                            ^^^^^^^^^^^^^^^^^ Don't stub your mock.
+    RUBY
+  end
+
+  it 'flags expect(...).to receive(...).and_return' do
+    expect_offense(<<-RUBY)
+      expect(foo).to receive(:bar).and_return("hello world")
+                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^ Don't stub your mock.
+    RUBY
+  end
+
+  it 'flags expect(...).to receive(...) { } ' do
+    expect_offense(<<-RUBY)
+      expect(foo).to receive(:bar) { "hello world" }
+                                   ^^^^^^^^^^^^^^^^^ Don't stub your mock.
+    RUBY
+  end
+
+  it 'approves of expect(...).to have_received' do
+    expect_no_offenses('expect(foo).to have_received(:bar)')
+  end
+end