class RuboCop::Cop::RSpec::ExpectChange
Checks for consistent style of change matcher.
Enforces either passing a receiver and message as method arguments, or a block.
This cop can be configured using the ‘EnforcedStyle` option.
@safety
Autocorrection is unsafe because `method_call` style calls the receiver *once* and sends the message to it before and after calling the `expect` block, whereas `block` style calls the expression *twice*, including the receiver. If your receiver is dynamic (e.g., the result of a method call) and you expect it to be called before and after the `expect` block, changing from `block` to `method_call` style may break your test. [source,ruby] ---- expect { run }.to change { my_method.message } # `my_method` is called before and after `run` expect { run }.to change(my_method, :message) # `my_method` is called once, but `message` is called on it twice ----
@example ‘EnforcedStyle: method_call` (default)
# bad expect { run }.to change { Foo.bar } expect { run }.to change { foo.baz } # good expect { run }.to change(Foo, :bar) expect { run }.to change(foo, :baz) # also good when there are arguments or chained method calls expect { run }.to change { Foo.bar(:count) } expect { run }.to change { user.reload.name }
@example ‘EnforcedStyle: block`
# bad expect { run }.to change(Foo, :bar) # good expect { run }.to change { Foo.bar }
Constants
- MSG_BLOCK
- MSG_CALL
- RESTRICT_ON_SEND
Public Instance Methods
Source
# File lib/rubocop/cop/rspec/expect_change.rb, line 91 def on_block(node) # rubocop:disable InternalAffairs/NumblockHandler return unless style == :method_call expect_change_with_block(node) do |receiver, message| msg = format(MSG_BLOCK, obj: receiver.source, attr: message) add_offense(node, message: msg) do |corrector| replacement = "change(#{receiver.source}, :#{message})" corrector.replace(node, replacement) end end end
Source
# File lib/rubocop/cop/rspec/expect_change.rb, line 79 def on_send(node) return unless style == :block expect_change_with_arguments(node) do |receiver, message| msg = format(MSG_CALL, obj: receiver.source, attr: message) add_offense(node, message: msg) do |corrector| replacement = "change { #{receiver.source}.#{message} }" corrector.replace(node, replacement) end end end