Module: RSpec::Matchers::DSL

Included in:
RSpec::Matchers
Defined in:
lib/rspec/matchers/dsl.rb

Overview

Defines the custom matcher DSL.

Defined Under Namespace

Modules: DefaultImplementations, Macros Classes: Matcher

Instance Method Summary (collapse)

Instance Method Details

- (Object) alias_matcher(new_name, old_name, options = {}) {|String| ... }

Defines a matcher alias. The returned matcher's description will be overriden to reflect the phrasing of the new name, which will be used in failure messages when passed as an argument to another matcher in a composed matcher expression.

Examples:

RSpec::Matchers.alias_matcher :a_list_that_sums_to, :sum_to
sum_to(3).description # => "sum to 3"
a_list_that_sums_to(3).description # => "a list that sums to 3"
RSpec::Matchers.alias_matcher :a_list_sorted_by, :be_sorted_by do |description|
  description.sub("be sorted by", "a list sorted by")
end
be_sorted_by(:age).description # => "be sorted by age"
a_list_sorted_by(:age).description # => "a list sorted by age"

Parameters:

  • new_name (Symbol) —

    the new name for the matcher

  • old_name (Symbol) —

    the original name for the matcher

  • options (Hash) (defaults to: {}) —

    options for the aliased matcher

Options Hash (options):

  • :klass (Class) —

    the ruby class to use as the decorator. (Not normally used).

Yields:

  • (String) —

    optional block that, when given, is used to define the overriden logic. The yielded arg is the original description or failure message. If no block is provided, a default override is used based on the old and new names.

See Also:

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# File 'lib/rspec/matchers/dsl.rb', line 30
def alias_matcher(new_name, old_name, options={}, &description_override)
  description_override ||= lambda do |old_desc|
    old_desc.gsub(EnglishPhrasing.split_words(old_name), EnglishPhrasing.split_words(new_name))
  end
  klass = options.fetch(:klass) { AliasedMatcher }
  define_method(new_name) do |*args, &block|
    matcher = __send__(old_name, *args, &block)
    matcher.matcher_name = new_name if matcher.respond_to?(:matcher_name=)
    klass.new(matcher, description_override)
  end
end

- (Object) define(name) {|Object| ... } Also known as: matcher

Defines a custom matcher.

Parameters:

  • name (Symbol) —

    the name for the matcher

Yields:

  • (Object) —

    block that is used to define the matcher. The block is evaluated in the context of your custom matcher class. When args are passed to your matcher, they will be yielded here, usually representing the expected value(s).

See Also:

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# File 'lib/rspec/matchers/dsl.rb', line 70
def define(name, &declarations)
  warn_about_block_args(name, declarations)
  define_method name do |*expected, &block_arg|
    RSpec::Matchers::DSL::Matcher.new(name, declarations, self, *expected, &block_arg)
  end
end

- (Object) define_negated_matcher(negated_name, base_name) {|String| ... }

Defines a negated matcher. The returned matcher's description and failure_message will be overriden to reflect the phrasing of the new name, and the match logic will be based on the original matcher but negated.

Examples:

RSpec::Matchers.define_negated_matcher :exclude, :include
include(1, 2).description # => "include 1 and 2"
exclude(1, 2).description # => "exclude 1 and 2"

Parameters:

  • negated_name (Symbol) —

    the name for the negated matcher

  • base_name (Symbol) —

    the name of the original matcher that will be negated

Yields:

  • (String) —

    optional block that, when given, is used to define the overriden logic. The yielded arg is the original description or failure message. If no block is provided, a default override is used based on the old and new names.

See Also:

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# File 'lib/rspec/matchers/dsl.rb', line 58
def define_negated_matcher(negated_name, base_name, &description_override)
  alias_matcher(negated_name, base_name, :klass => AliasedNegatedMatcher, &description_override)
end