Merge pull request #179 from rwstauner/rwstauner/assert-raises-regexp…

…-literal

Add cop to prevent regexp literals as arguments to assert_matches

changelog/new_add_cop_to_prevent_regexp_literals_as.md

@@ -0,0 +1 @@
+* [#179](https://github.com/rubocop/rubocop-minitest/pull/179): New `Minitest/AssertRaisesWithRegexpArgument` cop checks for regular expression literals passed to `assert_raises`. ([@rwstauner][])

config/default.yml

@@ -82,6 +82,11 @@ Minitest/AssertRaisesCompoundBody:
   Enabled: pending
   VersionAdded: '0.21'
 
+Minitest/AssertRaisesWithRegexpArgument:
+  Description: 'This cop enforces checks for regular expression literals passed to `assert_raises`.'
+  Enabled: pending
+  VersionAdded: '<<next>>'
+
 Minitest/AssertRespondTo:
   Description: 'This cop enforces the test to use `assert_respond_to(object, :do_something)` over `assert(object.respond_to?(:do_something))`.'
   StyleGuide: 'https://minitest.rubystyle.guide#assert-responds-to-method'

lib/rubocop/cop/minitest/assert_raises_with_regexp_argument.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Minitest
+      # Checks for `assert_raises` with arguments of regular expression literals.
+      # Arguments should be exception classes.
+      # Optionally the last argument can be a custom message string to help explain failures.
+      # Either way, it's not the argument that `exception.message` is compared to.
+      # The raised exception is returned and can be used
+      # to match against a regular expression.
+      #
+      # @example
+      #
+      #   # bad
+      #   assert_raises FooError, /some message/ do
+      #     obj.occur_error
+      #   end
+      #
+      #   # good
+      #   exception = assert_raises FooError do
+      #     obj.occur_error
+      #   end
+      #   assert_match(/some message/, exception.message)
+      #
+      class AssertRaisesWithRegexpArgument < Base
+        MSG = 'Do not pass regular expression literals to `assert_raises`. Test the resulting exception.'
+        RESTRICT_ON_SEND = %i[assert_raises].freeze
+
+        def on_send(node)
+          add_offense(node) if node.last_argument&.regexp_type?
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/minitest_cops.rb

@@ -12,6 +12,7 @@
 require_relative 'minitest/assert_in_delta'
 require_relative 'minitest/assert_predicate'
 require_relative 'minitest/assert_raises_compound_body'
+require_relative 'minitest/assert_raises_with_regexp_argument'
 require_relative 'minitest/assert_with_expected_argument'
 require_relative 'minitest/assertion_in_lifecycle_hook'
 require_relative 'minitest/assert_kind_of'

test/rubocop/cop/minitest/assert_raises_with_regexp_argument_test.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class AssertRaisesWithRegexpArgumentTest < Minitest::Test
+  def test_registers_offense_with_regexp
+    assert_offense(<<~RUBY)
+      assert_raises(MyError, /some message/) do
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Do not pass regular expression literals to `assert_raises`. Test the resulting exception.
+        foo
+      end
+    RUBY
+  end
+
+  def test_does_not_register_offense_with_other_args
+    assert_no_offenses(<<~RUBY)
+      assert_raises(MyError, SomeOtherError, some_local_var) do
+        foo
+      end
+    RUBY
+  end
+
+  def test_does_not_register_offense_with_single_arg
+    assert_no_offenses(<<~RUBY)
+      assert_raises(MyError) do
+        foo
+      end
+    RUBY
+  end
+end