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David Worth
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Add a cop to enforce expected exceptions to be specified
In order to avoid false-positives in the context of exception checking it is valuable to be able to enforce that each `to raise` pair to include specifying information about the type of exception.
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‎CHANGELOG.md

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* Fix `FactoryBot/AttributeDefinedStatically` not working when there is a non-symbol key. ([@vzvu3k6k][])
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* Fix false positive in `RSpec/ImplicitSubject` when `is_expected` is used inside `its()` block. ([@Darhazer][])
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* Add `single_statement_only` style to `RSpec/ImplicitSubject` as a more relaxed alternative to `single_line_only`. ([@Darhazer][])
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* Add `RSpec/UnspecifiedException` as a non-default cop to encourage more-specific `expect{}.to raise_error(ExceptionType)`, or `raise_exception` style handling of exceptions. ([@daveworth][])
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## 1.29.1 (2018-09-01)
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@@ -381,3 +382,4 @@ Compatibility release so users can upgrade RuboCop to 0.51.0. No new features.
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[@seanpdoyle]: https://github.com/seanpdoyle
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[@vzvu3k6k]: https://github.com/vzvu3k6k
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[@BrentWheeldon]: https://github.com/BrentWheeldon
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[@daveworth]: https://github.com/daveworth

‎config/default.yml

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Enabled: true
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StyleGuide: http://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/SubjectStub
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RSpec/UnspecifiedException:
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Description: Checks for a specified error in checking raised errors.
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Enabled: true
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StyleGuide: http://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/UnspecifiedException
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RSpec/VerifiedDoubles:
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Description: Prefer using verifying doubles over normal doubles.
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Enabled: true

‎lib/rubocop/cop/rspec/unspecified_exception.rb

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module RuboCop
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module Cop
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module RSpec
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# Checks for a specified error in checking raised errors.
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#
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# Enforces one of an Exception type, a string, or a regular
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# expression to match against the exception message as a parameter
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# to `raise_error`
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#
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# @example
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#
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# # bad
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# expect {
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# raise StandardError.new('error')
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# }.to raise_error
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#
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# # good
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# expect {
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# raise StandardError.new('error')
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# }.to raise_error(StandardError)
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#
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# expect {
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# raise StandardError.new('error')
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# }.to raise_error('error')
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#
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# expect {
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# raise StandardError.new('error')
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# }.to raise_error(/err/)
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#
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# expect { do_something }.not_to raise_error
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class UnspecifiedException < Cop
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MSG = 'Specify the exception being captured'.freeze
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def_node_matcher :empty_raise_error_or_exception, <<-PATTERN.freeze
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(send
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(block
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(send nil? :expect) ...)
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:to
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(send nil? {:raise_error :raise_exception})
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)
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PATTERN
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def on_send(node)
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return unless empty_exception_matcher?(node)
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add_offense(
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node.children.last,
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location: :expression
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)
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end
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def empty_exception_matcher?(node)
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empty_raise_error_or_exception(node) && !block_with_args?(node.parent)
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end
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def block_with_args?(node)
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return unless node && node.block_type?
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node.arguments?
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end
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end
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end
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end
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end

‎lib/rubocop/cop/rspec_cops.rb

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require_relative 'rspec/shared_examples'
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require_relative 'rspec/single_argument_message_chain'
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require_relative 'rspec/subject_stub'
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require_relative 'rspec/unspecified_exception'
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require_relative 'rspec/verified_doubles'
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require_relative 'rspec/void_expect'

‎manual/cops.md

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* [RSpec/SharedExamples](cops_rspec.md#rspecsharedexamples)
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* [RSpec/SingleArgumentMessageChain](cops_rspec.md#rspecsingleargumentmessagechain)
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* [RSpec/SubjectStub](cops_rspec.md#rspecsubjectstub)
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* [RSpec/UnspecifiedException](cops_rspec.md#rspecunspecifiedexception)
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* [RSpec/VerifiedDoubles](cops_rspec.md#rspecverifieddoubles)
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* [RSpec/VoidExpect](cops_rspec.md#rspecvoidexpect)
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‎manual/cops_rspec.md

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* [http://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/SubjectStub](http://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/SubjectStub)
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## RSpec/UnspecifiedException
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Enabled by default | Supports autocorrection
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--- | ---
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Enabled | No
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Checks for a specified error in checking raised errors.
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Enforces one of an Exception type, a string, or a regular
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expression to match against the exception message as a parameter
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to `raise_error`
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### Examples
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```ruby
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# bad
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expect {
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raise StandardError.new('error')
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}.to raise_error
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# good
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expect {
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raise StandardError.new('error')
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}.to raise_error(StandardError)
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expect {
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raise StandardError.new('error')
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}.to raise_error('error')
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expect {
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raise StandardError.new('error')
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}.to raise_error(/err/)
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expect { do_something }.not_to raise_error
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```
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### References
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* [http://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/UnspecifiedException](http://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/UnspecifiedException)
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## RSpec/VerifiedDoubles
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Enabled by default | Supports autocorrection

‎spec/rubocop/cop/rspec/unspecified_exception_spec.rb

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RSpec.describe RuboCop::Cop::RSpec::UnspecifiedException do
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subject(:cop) { described_class.new }
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context 'with raise_error matcher' do
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it 'detects the `unspecified_exception` offense' do
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expect_offense(<<-RUBY)
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expect {
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raise StandardError
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}.to raise_error
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^^^^^^^^^^^ Specify the exception being captured
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RUBY
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end
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it 'allows empty exception specification when not expecting an error' do
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expect_no_offenses(<<-RUBY)
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expect {
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raise StandardError
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}.not_to raise_error
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RUBY
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end
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it 'allows exception classes' do
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expect_no_offenses(<<-RUBY)
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expect {
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raise StandardError
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}.to raise_error(StandardError)
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RUBY
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end
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it 'allows exception messages' do
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expect_no_offenses(<<-RUBY)
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expect {
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raise StandardError.new('error')
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}.to raise_error('error')
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RUBY
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end
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it 'allows exception types with messages' do
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expect_no_offenses(<<-RUBY)
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expect {
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raise StandardError.new('error')
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}.to raise_error(StandardError, 'error')
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RUBY
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end
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it 'allows exception matching regular expressions' do
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expect_no_offenses(<<-RUBY)
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expect {
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raise StandardError.new('error')
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}.to raise_error(/err/)
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RUBY
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end
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it 'allows exception types with matching regular expressions' do
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expect_no_offenses(<<-RUBY)
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expect {
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raise StandardError.new('error')
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}.to raise_error(StandardError, /err/)
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RUBY
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end
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it 'allows classes with blocks with braces' do
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expect_no_offenses(<<-RUBY)
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expect {
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raise StandardError.new('error')
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}.to raise_error { |err| err.data }
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RUBY
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end
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it 'allows classes with blocks with do/end' do
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expect_no_offenses(<<-RUBY)
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expect {
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raise StandardError.new('error')
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}.to raise_error do |error|
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error.data
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end
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RUBY
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end
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it 'allows parameterized exceptions' do
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expect_no_offenses(<<-RUBY)
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my_exception = StandardError.new('my exception')
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expect {
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raise my_exception
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}.to raise_error(my_exception)
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RUBY
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end
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end
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context 'with raise_exception matcher' do
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it 'detects the `unspecified_exception` offense' do
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expect_offense(<<-RUBY)
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expect {
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raise StandardError
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}.to raise_exception
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^^^^^^^^^^^^^^^ Specify the exception being captured
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RUBY
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end
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it 'allows empty exception specification when not expecting an error' do
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expect_no_offenses(<<-RUBY)
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expect {
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raise StandardError
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}.not_to raise_exception
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RUBY
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end
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it 'allows exception classes' do
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expect_no_offenses(<<-RUBY)
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expect {
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raise StandardError
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}.to raise_exception(StandardError)
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RUBY
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end
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it 'allows exception messages' do
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expect_no_offenses(<<-RUBY)
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expect {
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raise StandardError.new('error')
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}.to raise_exception('error')
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RUBY
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end
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it 'allows exception types with messages' do
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expect_no_offenses(<<-RUBY)
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expect {
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raise StandardError.new('error')
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}.to raise_exception(StandardError, 'error')
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RUBY
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end
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it 'allows exception matching regular expressions' do
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expect_no_offenses(<<-RUBY)
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expect {
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raise StandardError.new('error')
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}.to raise_exception(/err/)
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RUBY
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end
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it 'allows exception types with matching regular expressions' do
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expect_no_offenses(<<-RUBY)
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expect {
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raise StandardError.new('error')
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}.to raise_exception(StandardError, /err/)
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RUBY
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end
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it 'allows classes with blocks with braces' do
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expect_no_offenses(<<-RUBY)
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expect {
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raise StandardError.new('error')
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}.to raise_exception { |err| err.data }
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RUBY
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end
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it 'allows classes with blocks with do/end' do
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expect_no_offenses(<<-RUBY)
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expect {
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raise StandardError.new('error')
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}.to raise_exception do |error|
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error.data
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end
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RUBY
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end
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it 'allows parameterized exceptions' do
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expect_no_offenses(<<-RUBY)
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my_exception = StandardError.new('my exception')
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expect {
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raise my_exception
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}.to raise_exception(my_exception)
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RUBY
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end
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end
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end

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