Module: RSpec::Matchers

Extended by:
DSL
Included in:
DSL::Matcher
Defined in:
lib/rspec/matchers.rb,
lib/rspec/matchers/dsl.rb,
lib/rspec/matchers/built_in.rb,
lib/rspec/matchers/composable.rb,
lib/rspec/matchers/built_in/be.rb,
lib/rspec/matchers/built_in/eq.rb,
lib/rspec/matchers/built_in/all.rb,
lib/rspec/matchers/built_in/eql.rb,
lib/rspec/matchers/built_in/has.rb,
lib/rspec/matchers/fail_matchers.rb,
lib/rspec/matchers/built_in/cover.rb,
lib/rspec/matchers/built_in/equal.rb,
lib/rspec/matchers/built_in/exist.rb,
lib/rspec/matchers/built_in/match.rb,
lib/rspec/matchers/built_in/yield.rb,
lib/rspec/matchers/aliased_matcher.rb,
lib/rspec/matchers/built_in/change.rb,
lib/rspec/matchers/built_in/output.rb,
lib/rspec/matchers/built_in/include.rb,
lib/rspec/matchers/built_in/satisfy.rb,
lib/rspec/matchers/english_phrasing.rb,
lib/rspec/matchers/matcher_protocol.rb,
lib/rspec/matchers/built_in/compound.rb,
lib/rspec/matchers/matcher_delegator.rb,
lib/rspec/matchers/built_in/be_within.rb,
lib/rspec/matchers/built_in/operators.rb,
lib/rspec/matchers/multi_matcher_diff.rb,
lib/rspec/matchers/built_in/be_between.rb,
lib/rspec/matchers/built_in/be_kind_of.rb,
lib/rspec/matchers/built_in/respond_to.rb,
lib/rspec/matchers/built_in/raise_error.rb,
lib/rspec/matchers/built_in/base_matcher.rb,
lib/rspec/matchers/built_in/throw_symbol.rb,
lib/rspec/matchers/generated_descriptions.rb,
lib/rspec/matchers/built_in/be_instance_of.rb,
lib/rspec/matchers/built_in/contain_exactly.rb,
lib/rspec/matchers/built_in/have_attributes.rb,
lib/rspec/matchers/built_in/count_expectation.rb,
lib/rspec/matchers/built_in/start_or_end_with.rb

Overview

RSpec::Matchers provides a number of useful matchers we use to define expectations. Any object that implements the matcher protocol can be used as a matcher.

Predicates

In addition to matchers that are defined explicitly, RSpec will create custom matchers on the fly for any arbitrary predicate, giving your specs a much more natural language feel.

A Ruby predicate is a method that ends with a "?" and returns true or false. Common examples are empty?, nil?, and instance_of?.

All you need to do is write expect(..).to be_ followed by the predicate without the question mark, and RSpec will figure it out from there. For example:

expect([]).to be_empty     # => [].empty?() | passes
expect([]).not_to be_empty # => [].empty?() | fails

In addition to prefixing the predicate matchers with "be_", you can also use "be_a_" and "be_an_", making your specs read much more naturally:

expect("a string").to be_an_instance_of(String) # =>"a string".instance_of?(String) # passes

expect(3).to be_a_kind_of(Integer)          # => 3.kind_of?(Numeric)     | passes
expect(3).to be_a_kind_of(Numeric)          # => 3.kind_of?(Numeric)     | passes
expect(3).to be_an_instance_of(Integer)     # => 3.instance_of?(Integer) | passes
expect(3).not_to be_an_instance_of(Numeric) # => 3.instance_of?(Numeric) | fails

RSpec will also create custom matchers for predicates like has_key?. To use this feature, just state that the object should have_key(:key) and RSpec will call has_key?(:key) on the target. For example:

expect(:a => "A").to have_key(:a)
expect(:a => "A").to have_key(:b) # fails

You can use this feature to invoke any predicate that begins with "has_", whether it is part of the Ruby libraries (like Hash#has_key?) or a method you wrote on your own class.

Note that RSpec does not provide composable aliases for these dynamic predicate matchers. You can easily define your own aliases, though:

RSpec::Matchers.alias_matcher :a_user_who_is_an_admin, :be_an_admin
expect(user_list).to include(a_user_who_is_an_admin)

Alias Matchers

With Matchers.alias_matcher, you can easily create an alternate name for a given matcher.

The description will also change according to the new name:

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"

or you can specify a custom description like this:

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"

Custom Matchers

When you find that none of the stock matchers provide a natural feeling expectation, you can very easily write your own using RSpec's matcher DSL or writing one from scratch.

Matcher DSL

Imagine that you are writing a game in which players can be in various zones on a virtual board. To specify that bob should be in zone 4, you could say:

expect(bob.current_zone).to eql(Zone.new("4"))

But you might find it more expressive to say:

expect(bob).to be_in_zone("4")

and/or

expect(bob).not_to be_in_zone("3")

You can create such a matcher like so:

RSpec::Matchers.define :be_in_zone do |zone|
  match do |player|
    player.in_zone?(zone)
  end
end

This will generate a be_in_zone method that returns a matcher with logical default messages for failures. You can override the failure messages and the generated description as follows:

RSpec::Matchers.define :be_in_zone do |zone|
  match do |player|
    player.in_zone?(zone)
  end
  failure_message do |player|
    # generate and return the appropriate string.
  end
  failure_message_when_negated do |player|
    # generate and return the appropriate string.
  end
  description do
    # generate and return the appropriate string.
  end
end

Each of the message-generation methods has access to the block arguments passed to the create method (in this case, zone). The failure message methods (failure_message and failure_message_when_negated) are passed the actual value (the receiver of expect(..) or expect(..).not_to).

Custom Matcher from scratch

You could also write a custom matcher from scratch, as follows:

class BeInZone
  def initialize(expected)
    @expected = expected
  end
  def matches?(target)
    @target = target
    @target.current_zone.eql?(Zone.new(@expected))
  end
  def failure_message
    "expected #{@target.inspect} to be in Zone #{@expected}"
  end
  def failure_message_when_negated
    "expected #{@target.inspect} not to be in Zone #{@expected}"
  end
end

... and a method like this:

def be_in_zone(expected)
  BeInZone.new(expected)
end

And then expose the method to your specs. This is normally done by including the method and the class in a module, which is then included in your spec:

module CustomGameMatchers
  class BeInZone
    # ...
  end
  def be_in_zone(expected)
    # ...
  end
end
describe "Player behaviour" do
  include CustomGameMatchers
  # ...
end

or you can include in globally in a spec_helper.rb file required from your spec file(s):

RSpec::configure do |config|
  config.include(CustomGameMatchers)
end

Making custom matchers composable

RSpec's built-in matchers are designed to be composed, in expressions like:

expect(["barn", 2.45]).to contain_exactly(
  a_value_within(0.1).of(2.5),
  a_string_starting_with("bar")
)

Custom matchers can easily participate in composed matcher expressions like these. Include Composable in your custom matcher to make it support being composed (matchers defined using the DSL have this included automatically). Within your matcher's matches? method (or the match block, if using the DSL), use values_match?(expected, actual) rather than expected == actual. Under the covers, values_match? is able to match arbitrary nested data structures containing a mix of both matchers and non-matcher objects. It uses === and == to perform the matching, considering the values to match if either returns true. The Composable mixin also provides some helper methods for surfacing the matcher descriptions within your matcher's description or failure messages.

RSpec's built-in matchers each have a number of aliases that rephrase the matcher from a verb phrase (such as be_within) to a noun phrase (such as a_value_within), which reads better when the matcher is passed as an argument in a composed matcher expressions, and also uses the noun-phrase wording in the matcher's description, for readable failure messages. You can alias your custom matchers in similar fashion using Matchers.alias_matcher.

Negated Matchers

Sometimes if you want to test for the opposite using a more descriptive name instead of using not_to, you can use Matchers.define_negated_matcher:

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

While the most obvious negated form may be to add a not_ prefix, the failure messages you get with that form can be confusing (e.g. "expected [actual] to not [verb], but did not"). We've found it works best to find a more positive name for the negated form, such as avoid_changing rather than not_change.

Defined Under Namespace

Modules: BuiltIn, Composable, DSL, EnglishPhrasing, FailMatchers Classes: AliasedMatcher, MatcherProtocol, MultiMatcherDiff

Class Method Summary collapse

Instance Method Summary collapse

Methods included from DSL

alias_matcher, define, define_negated_matcher

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(method, *args, &block) ⇒ Object (private) 

961
962
963
964
965
966
967
968
969
970
 
# File 'lib/rspec/matchers.rb', line 961
def method_missing(method, *args, &block)
  case method.to_s
  when BE_PREDICATE_REGEX
    BuiltIn::BePredicate.new(method, *args, &block)
  when HAS_REGEX
    BuiltIn::Has.new(method, *args, &block)
  else
    super
  end
end

Class Method Details

.alias_matcher(new_name, old_name, options = {}, &description_override) ⇒ Object

Extended from RSpec::Matchers::DSL#alias_matcher.

250
251
252
 
# File 'lib/rspec/matchers.rb', line 250
def self.alias_matcher(*args, &block)
  super(*args, &block)
end

.clear_generated_description ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Used by rspec-core to clear the state used to generate descriptions after an example.

11
12
13
14
 
# File 'lib/rspec/matchers/generated_descriptions.rb', line 11
def self.clear_generated_description
  self.last_matcher = nil
  self.last_expectation_handler = nil
end

.configuration ⇒ RSpec::Expectations::Configuration

Delegates to Expectations.configuration. This is here because rspec-core's expect_with option looks for a configuration method on the mixin (RSpec::Matchers) to yield to a block.

Returns:

951
952
953
 
# File 'lib/rspec/matchers.rb', line 951
def self.configuration
  Expectations.configuration
end

.define(name, &declarations) ⇒ Object

Extended from RSpec::Matchers::DSL#define.


    		
    
      
# File 'lib/rspec/matchers.rb', line 257


    		
  





      

  

    .define_negated_matcher(negated_name, base_name, &description_override)  ⇒ Object 


  

    
Extended from RSpec::Matchers::DSL#define_negated_matcher.

  







  

    
      

    		
    
      
# File 'lib/rspec/matchers.rb', line 260


    		
  





      

  

    .generated_description  ⇒ Object 


  

    

  This method is part of a private API.
  You should avoid using this method if possible, as it may be removed or be changed in the future.



Generates an an example description based on the last expectation.
Used by rspec-core's one-liner syntax.

  







  

    
      
19
20
21
22

    		
    
      
# File 'lib/rspec/matchers/generated_descriptions.rb', line 19
def self.generated_description
  return nil if last_expectation_handler.nil?
  "#{last_expectation_handler.verb} #{last_description}"
end

    		
  





  

  

    
Instance Method Details

      

  

    #aggregate_failures(label = nil, metadata = {}) { ... } ⇒ Object 


  

  

    Note:
    
The implementation of this feature uses a thread-local variable,
which means that if you have an expectation failure in another thread,
it'll abort like normal.



  


Allows multiple expectations in the provided block to fail, and then
aggregates them into a single exception, rather than aborting on the
first expectation failure like normal. This allows you to see all
failures from an entire set of expectations without splitting each
off into its own example (which may slow things down if the example
setup is expensive).

  





  

    
Examples:

      
aggregate_failures("verifying response") do
  expect(response.status).to eq(200)
  expect(response.headers).to include("Content-Type" => "text/plain")
  expect(response.body).to include("Success")
end

  


Parameters:


    
    
  • 
        label
        (String)
        (defaults to: nil)
        —
        
    label for this aggregation block, which will be
included in the aggregated exception message.
    

    
    
    • 
    
  • 
        metadata
        (Hash)
        (defaults to: {})
        —
        
    additional metadata about this failure aggregation
block. If multiple expectations fail, it will be exposed from the
Expectations::MultipleExpectationsNotMetError exception. Mostly
intended for internal RSpec use but you can use it as well.
    

    
    
    • 



Yields:


    
    
  • 
        
        
    Block containing as many expectation as you want. The block is
simply yielded to, so you can trust that anything that works outside
the block should work within it.
    

    
    
    • 



Raises:




  

    
      
305
306
307

    		
    
      
# File 'lib/rspec/matchers.rb', line 305
def aggregate_failures(label=nil, metadata={}, &block)
  Expectations::FailureAggregator.new(label, metadata).aggregate(&block)
end

    		
  





      

  

    #all(expected)  ⇒ Object 


  

  

    Note:
    
The negative form not_to all is not supported. Instead
use not_to include or pass a negative form of a matcher
as the argument (e.g. all exclude(:foo)).



  

  

    Note:
    
You can also use this with compound matchers as well.



  


Passes if the provided matcher passes when checked against all
elements of the collection.

  





  

    
Examples:

      
expect([1, 3, 5]).to all be_odd
expect([1, 3, 6]).to all be_odd # fails

      
expect([1, 3, 5]).to all( be_odd.and be_an(Integer) )

  



  

    
      
662
663
664

    		
    
      
# File 'lib/rspec/matchers.rb', line 662
def all(expected)
  BuiltIn::All.new(expected)
end

    		
  





      

  

    #be(*args)  ⇒ Object 
    Also known as:
    a_value
    


  

    
Given true, false, or nil, will pass if actual value is true, false or
nil (respectively). Given no args means the caller should satisfy an if
condition (to be or not to be).


Predicates are any Ruby method that ends in a "?" and returns true or
false.  Given be_ followed by arbitrary_predicate (without the "?"),
RSpec will match convert that into a query against the target object.


The arbitrary_predicate feature will handle any predicate prefixed with
"be_an_" (e.g. be_an_instance_of), "be_a_" (e.g. be_a_kind_of) or "be_"
(e.g. be_empty), letting you choose the prefix that best suits the
predicate.

  





  

    
Examples:

      
expect(actual).to     be_truthy
expect(actual).to     be_falsey
expect(actual).to     be_nil
expect(actual).to     be_[arbitrary_predicate](*args)
expect(actual).not_to be_nil
expect(actual).not_to be_[arbitrary_predicate](*args)

  



  

    
      
349
350
351

    		
    
      
# File 'lib/rspec/matchers.rb', line 349
def be(*args)
  args.empty? ? Matchers::BuiltIn::Be.new : equal(*args)
end

    		
  





      

  

    #be_a(klass)  ⇒ Object 
    Also known as:
    be_an
    


  

    
passes if target.kind_of?(klass)

  







  

    
      
355
356
357

    		
    
      
# File 'lib/rspec/matchers.rb', line 355
def be_a(klass)
  be_a_kind_of(klass)
end

    		
  





      

  

    #be_a_kind_of(expected)  ⇒ Object 
    Also known as:
    be_kind_of, a_kind_of
    


  

    
Passes if actual.kind_of?(expected)

  





  

    
Examples:

      
expect(5).to     be_a_kind_of(Integer)
expect(5).to     be_a_kind_of(Numeric)
expect(5).not_to be_a_kind_of(Float)

  



  

    
      
378
379
380

    		
    
      
# File 'lib/rspec/matchers.rb', line 378
def be_a_kind_of(expected)
  BuiltIn::BeAKindOf.new(expected)
end

    		
  





      

  

    #be_an_instance_of(expected)  ⇒ Object 
    Also known as:
    be_instance_of, an_instance_of
    


  

    
Passes if actual.instance_of?(expected)

  





  

    
Examples:

      
expect(5).to     be_an_instance_of(Integer)
expect(5).not_to be_an_instance_of(Numeric)
expect(5).not_to be_an_instance_of(Float)

  



  

    
      
366
367
368

    		
    
      
# File 'lib/rspec/matchers.rb', line 366
def be_an_instance_of(expected)
  BuiltIn::BeAnInstanceOf.new(expected)
end

    		
  





      

  

    #be_between(min, max)  ⇒ Object 
    Also known as:
    a_value_between
    


  

    
Passes if actual.between?(min, max). Works with any Comparable object,
including String, Symbol, Time, or Numeric (Fixnum, Bignum, Integer,
Float, Complex, and Rational).


By default, be_between is inclusive (i.e. passes when given either the max or min value),
but you can make it exclusive by chaining that off the matcher.

  





  

    
Examples:

      
expect(5).to      be_between(1, 10)
expect(11).not_to be_between(1, 10)
expect(10).not_to be_between(1, 10).exclusive

  



  

    
      
395
396
397

    		
    
      
# File 'lib/rspec/matchers.rb', line 395
def be_between(min, max)
  BuiltIn::BeBetween.new(min, max)
end

    		
  





      

  

    #be_falsey  ⇒ Object 
    Also known as:
    be_falsy, a_falsey_value, a_falsy_value
    


  

    
Passes if actual is falsey (false or nil)

  







  

    
      
316
317
318

    		
    
      
# File 'lib/rspec/matchers.rb', line 316
def be_falsey
  BuiltIn::BeFalsey.new
end

    		
  





      

  

    #be_nil  ⇒ Object 
    Also known as:
    a_nil_value
    


  

    
Passes if actual is nil

  







  

    
      
324
325
326

    		
    
      
# File 'lib/rspec/matchers.rb', line 324
def be_nil
  BuiltIn::BeNil.new
end

    		
  





      

  

    #be_truthy  ⇒ Object 
    Also known as:
    a_truthy_value
    


  

    
Passes if actual is truthy (anything but false or nil)

  







  

    
      
310
311
312

    		
    
      
# File 'lib/rspec/matchers.rb', line 310
def be_truthy
  BuiltIn::BeTruthy.new
end

    		
  





      

  

    #be_within(delta)  ⇒ Object 
    Also known as:
    a_value_within, within
    


  

    
Passes if actual == expected +/- delta

  





  

    
Examples:

      
expect(result).to     be_within(0.5).of(3.0)
expect(result).not_to be_within(0.5).of(3.0)

  



  

    
      
405
406
407

    		
    
      
# File 'lib/rspec/matchers.rb', line 405
def be_within(delta)
  BuiltIn::BeWithin.new(delta)
end

    		
  





      

  

    #change(receiver = nil, message = nil, &block)  ⇒ Object 
    Also known as:
    a_block_changing, changing
    


  

    
Applied to a proc, specifies that its execution will cause some value to
change.


You can either pass receiver and message, or a block,
but not both.


When passing a block, it must use the { ... } format, not
do/end, as { ... } binds to the change method, whereas do/end
would errantly bind to the expect(..).to or expect(...).not_to method.


You can chain any of the following off of the end to specify details
about the change:


    

  • from
    • 

  • to
    • 



or any one of:


    

  • by
    • 

  • by_at_least
    • 

  • by_at_most
    • 



== Notes


Evaluates receiver.message or block before and after it
evaluates the block passed to expect. If the value is the same
object, its before/after hash value is used to see if it has changed.
Therefore, your object needs to properly implement hash to work correctly
with this matcher.


expect( ... ).not_to change supports the form that specifies from
(which specifies what you expect the starting, unchanged value to be)
but does not support forms with subsequent calls to by, by_at_least,
by_at_most or to.

  





  

    
Examples:

      
expect {
  team.add_player(player)
}.to change(roster, :count)
expect {
  team.add_player(player)
}.to change(roster, :count).by(1)
expect {
  team.add_player(player)
}.to change(roster, :count).by_at_least(1)
expect {
  team.add_player(player)
}.to change(roster, :count).by_at_most(1)
string = "string"
expect {
  string.reverse!
}.to change { string }.from("string").to("gnirts")
string = "string"
expect {
  string
}.not_to change { string }.from("string")
expect {
  person.happy_birthday
}.to change(person, :birthday).from(32).to(33)
expect {
  employee.develop_great_new_social_networking_app
}.to change(employee, :title).from("Mail Clerk").to("CEO")
expect {
  doctor.leave_office
}.to change(doctor, :sign).from(/is in/).to(/is out/)
user = User.new(:type => "admin")
expect {
  user.symbolize_type
}.to change(user, :type).from(String).to(Symbol)

  


Parameters:


    
    
  • 
        receiver
        (Object)
        (defaults to: nil)
    
    • 
    
  • 
        message
        (Symbol)
        (defaults to: nil)
        —
        
    the message to send the receiver
    

    
    
    • 




  

    
      
492
493
494

    		
    
      
# File 'lib/rspec/matchers.rb', line 492
def change(receiver=nil, message=nil, &block)
  BuiltIn::Change.new(receiver, message, &block)
end

    		
  





      

  

    #contain_exactly(*items)  ⇒ Object 
    Also known as:
    a_collection_containing_exactly, containing_exactly
    


  

  

    Note:
    
This is also available using the =~ operator with should,
but =~ is not supported with expect.



  


Passes if actual contains all of the expected regardless of order.
This works for collections. Pass in multiple args and it will only
pass if all args are found in collection.

  





  

    
Examples:

      
expect([1, 2, 3]).to contain_exactly(1, 2, 3)
expect([1, 2, 3]).to contain_exactly(1, 3, 2)

  

  
See Also:

  


  

    
      
510
511
512

    		
    
      
# File 'lib/rspec/matchers.rb', line 510
def contain_exactly(*items)
  BuiltIn::ContainExactly.new(items)
end

    		
  





      

  

    #cover(*values)  ⇒ Object 
    Also known as:
    a_range_covering, covering
    


  

    
Passes if actual covers expected. This works for
Ranges. You can also pass in multiple args
and it will only pass if all args are found in Range.


Warning:: Ruby >= 1.9 only

  





  

    
Examples:

      
expect(1..10).to     cover(5)
expect(1..10).to     cover(4, 6)
expect(1..10).to     cover(4, 6, 11) # fails
expect(1..10).not_to cover(11)
expect(1..10).not_to cover(5)        # fails

  



  

    
      
528
529
530

    		
    
      
# File 'lib/rspec/matchers.rb', line 528
def cover(*values)
  BuiltIn::Cover.new(*values)
end

    		
  





      

  

    #end_with(*expected)  ⇒ Object 
    Also known as:
    a_collection_ending_with, a_string_ending_with, ending_with
    


  

    
Matches if the actual value ends with the expected value(s). In the case
of a string, matches against the last expected.length characters of the
actual string. In the case of an array, matches against the last
expected.length elements of the actual array.

  





  

    
Examples:

      
expect("this string").to   end_with "string"
expect([0, 1, 2, 3, 4]).to end_with 4
expect([0, 2, 3, 4, 4]).to end_with 3, 4

  



  

    
      
543
544
545

    		
    
      
# File 'lib/rspec/matchers.rb', line 543
def end_with(*expected)
  BuiltIn::EndWith.new(*expected)
end

    		
  





      

  

    #eq(expected)  ⇒ Object 
    Also known as:
    an_object_eq_to, eq_to
    


  

    
Passes if actual == expected.


See http://www.ruby-doc.org/core/classes/Object.html#M001057 for more
information about equality in Ruby.

  





  

    
Examples:

      
expect(5).to     eq(5)
expect(5).not_to eq(3)

  



  

    
      
558
559
560

    		
    
      
# File 'lib/rspec/matchers.rb', line 558
def eq(expected)
  BuiltIn::Eq.new(expected)
end

    		
  





      

  

    #eql(expected)  ⇒ Object 
    Also known as:
    an_object_eql_to, eql_to
    


  

    
Passes if actual.eql?(expected)


See http://www.ruby-doc.org/core/classes/Object.html#M001057 for more
information about equality in Ruby.

  





  

    
Examples:

      
expect(5).to     eql(5)
expect(5).not_to eql(3)

  



  

    
      
572
573
574

    		
    
      
# File 'lib/rspec/matchers.rb', line 572
def eql(expected)
  BuiltIn::Eql.new(expected)
end

    		
  





      

  

    #equal(expected)  ⇒ Object 
    Also known as:
    an_object_equal_to, equal_to
    


  

    
Passes if actual.equal?(expected) (object identity).


See http://www.ruby-doc.org/core/classes/Object.html#M001057 for more
information about equality in Ruby.

  





  

    
Examples:

      
expect(5).to       equal(5)   # Integers are equal
expect("5").not_to equal("5") # Strings that look the same are not the same object

  



  

    
      
586
587
588

    		
    
      
# File 'lib/rspec/matchers.rb', line 586
def equal(expected)
  BuiltIn::Equal.new(expected)
end

    		
  





      

  

    #exist(*args)  ⇒ Object 
    Also known as:
    an_object_existing, existing
    


  

    
Passes if actual.exist? or actual.exists?

  





  

    
Examples:

      
expect(File).to exist("path/to/file")

  



  

    
      
596
597
598

    		
    
      
# File 'lib/rspec/matchers.rb', line 596
def exist(*args)
  BuiltIn::Exist.new(*args)
end

    		
  





      

  

    #expect  ⇒ Expectations::ExpectationTarget 


  

    
Supports expect(actual).to matcher syntax by wrapping actual in an
ExpectationTarget.

  





  

    
Examples:

      
expect(actual).to eq(expected)
expect(actual).not_to eq(expected)

  


Returns:


  
See Also:

  


  

    
      

    		
    
      
# File 'lib/rspec/matchers.rb', line 263


    		
  





      

  

    #have_attributes(expected)  ⇒ Object 
    Also known as:
    an_object_having_attributes, having_attributes
    


  

  

    Note:
    
It will fail if actual doesn't respond to any of the expected attributes.



  


Passes if actual's attribute values match the expected attributes hash.
This works no matter how you define your attribute readers.

  





  

    
Examples:

      
Person = Struct.new(:name, :age)
person = Person.new("Bob", 32)
expect(person).to have_attributes(:name => "Bob", :age => 32)
expect(person).to have_attributes(:name => a_string_starting_with("B"), :age => (a_value > 30) )

      
expect(person).to have_attributes(:color => "red")

  



  

    
      
616
617
618

    		
    
      
# File 'lib/rspec/matchers.rb', line 616
def have_attributes(expected)
  BuiltIn::HaveAttributes.new(expected)
end

    		
  





      

  

    #include(*expected)  ⇒ Object 
    Also known as:
    a_collection_including, a_string_including, a_hash_including, including
    


  

    
Passes if actual includes expected. This works for
collections and Strings. You can also pass in multiple args
and it will only pass if all args are found in collection.

  





  

    
Examples:

      
expect([1,2,3]).to      include(3)
expect([1,2,3]).to      include(2,3)
expect([1,2,3]).to      include(2,3,4) # fails
expect([1,2,3]).not_to  include(4)
expect("spread").to     include("read")
expect("spread").not_to include("red")
expect(:a => 1, :b => 2).to include(:a)
expect(:a => 1, :b => 2).to include(:a, :b)
expect(:a => 1, :b => 2).to include(:a => 1)
expect(:a => 1, :b => 2).to include(:b => 2, :a => 1)
expect(:a => 1, :b => 2).to include(:c) # fails
expect(:a => 1, :b => 2).not_to include(:a => 2)

  



  

    
      
639
640
641

    		
    
      
# File 'lib/rspec/matchers.rb', line 639
def include(*expected)
  BuiltIn::Include.new(*expected)
end

    		
  





      

  

    #match(expected)  ⇒ Object 
    Also known as:
    match_regex, an_object_matching, a_string_matching, matching
    


  

  

    Note:
    
The match_regex alias is deprecated and is not recommended for use.
It was added in 2.12.1 to facilitate its use from within custom
matchers (due to how the custom matcher DSL was evaluated in 2.x,
match could not be used there), but is no longer needed in 3.x.



  


Given a Regexp or String, passes if actual.match(pattern)
Given an arbitrary nested data structure (e.g. arrays and hashes),
matches if expected === actual || actual == expected for each
pair of elements.

  





  

    
Examples:

      
expect(email).to match(/^([^\s]+)((?:[-a-z0-9]+\.)+[a-z]{2,})$/i)
expect(email).to match("@example.com")

      
hash = {
  :a => {
    :b => ["foo", 5],
    :c => { :d => 2.05 }
  }
}
expect(hash).to match(
  :a => {
    :b => a_collection_containing_exactly(
      a_string_starting_with("f"),
      an_instance_of(Integer)
    ),
    :c => { :d => (a_value < 3) }
  }
)

  



  

    
      
697
698
699

    		
    
      
# File 'lib/rspec/matchers.rb', line 697
def match(expected)
  BuiltIn::Match.new(expected)
end

    		
  





      

  

    #match_array(items)  ⇒ Object 
    Also known as:
    an_array_matching
    


  

    
An alternate form of contain_exactly that accepts
the expected contents as a single array arg rather
than splatted out as individual items.

  





  

    
Examples:

      
expect(results).to contain_exactly(1, 2)
# is identical to:
expect(results).to match_array([1, 2])

  

  
See Also:

  


  

    
      
715
716
717

    		
    
      
# File 'lib/rspec/matchers.rb', line 715
def match_array(items)
  contain_exactly(*items)
end

    		
  





      

  

    #output(expected = nil)  ⇒ Object 
    Also known as:
    a_block_outputting
    


  

  

    Note:
    
to_stdout and to_stderr work by temporarily replacing $stdout or $stderr,
so they're not able to intercept stream output that explicitly uses STDOUT/STDERR
or that uses a reference to $stdout/$stderr that was stored before the
matcher was used.



  

  

    Note:
    
to_stdout_from_any_process and to_stderr_from_any_process use Tempfiles, and
are thus significantly (~30x) slower than to_stdout and to_stderr.



  


With no arg, passes if the block outputs to_stdout or to_stderr.
With a string, passes if the block outputs that specific string to_stdout or to_stderr.
With a regexp or matcher, passes if the block outputs a string to_stdout or to_stderr that matches.


To capture output from any spawned subprocess as well, use to_stdout_from_any_process or
to_stderr_from_any_process. Output from any process that inherits the main process's corresponding
standard stream will be captured.

  





  

    
Examples:

      
expect { print 'foo' }.to output.to_stdout
expect { print 'foo' }.to output('foo').to_stdout
expect { print 'foo' }.to output(/foo/).to_stdout
expect { do_something }.to_not output.to_stdout
expect { warn('foo') }.to output.to_stderr
expect { warn('foo') }.to output('foo').to_stderr
expect { warn('foo') }.to output(/foo/).to_stderr
expect { do_something }.to_not output.to_stderr
expect { system('echo foo') }.to output("foo\n").to_stdout_from_any_process
expect { system('echo foo', out: :err) }.to output("foo\n").to_stderr_from_any_process

  



  

    
      
752
753
754

    		
    
      
# File 'lib/rspec/matchers.rb', line 752
def output(expected=nil)
  BuiltIn::Output.new(expected)
end

    		
  





      

  

    #raise_error(error = BuiltIn::RaiseError::UndefinedValue, message = nil, &block)  ⇒ Object 
    Also known as:
    raise_exception, a_block_raising, raising
    


  

    
With no args, matches if any error is raised.
With a named error, matches only if that specific error is raised.
With a named error and message specified as a String, matches only if both match.
With a named error and message specified as a Regexp, matches only if both match.
Pass an optional block to perform extra verifications on the exception matched

  





  

    
Examples:

      
expect { do_something_risky }.to raise_error
expect { do_something_risky }.to raise_error(PoorRiskDecisionError)
expect { do_something_risky }.to raise_error(PoorRiskDecisionError) { |error| expect(error.data).to eq 42 }
expect { do_something_risky }.to raise_error { |error| expect(error.data).to eq 42 }
expect { do_something_risky }.to raise_error(PoorRiskDecisionError, "that was too risky")
expect { do_something_risky }.to raise_error(PoorRiskDecisionError, /oo ri/)
expect { do_something_risky }.to raise_error("that was too risky")
expect { do_something_risky }.not_to raise_error

  



  

    
      
773
774
775

    		
    
      
# File 'lib/rspec/matchers.rb', line 773
def raise_error(error=BuiltIn::RaiseError::UndefinedValue, message=nil, &block)
  BuiltIn::RaiseError.new(error, message, &block)
end

    		
  





      

  

    #respond_to(*names)  ⇒ Object 
    Also known as:
    an_object_responding_to, responding_to
    


  

    
Matches if the target object responds to all of the names
provided. Names can be Strings or Symbols.

  





  

    
Examples:

      
expect("string").to respond_to(:length)

  



  

    
      
792
793
794

    		
    
      
# File 'lib/rspec/matchers.rb', line 792
def respond_to(*names)
  BuiltIn::RespondTo.new(*names)
end

    		
  





      

  

    #respond_to?(method)  ⇒ Boolean 


  

    
:nocov:

  






Returns:


    
    
  • 
        (Boolean)
    
    • 




  

    
      
979
980
981
982

    		
    
      
# File 'lib/rspec/matchers.rb', line 979
def respond_to?(method, *)
  method = method.to_s
  method =~ DYNAMIC_MATCHER_REGEX || super
end

    		
  





      

  

    #satisfy(description = nil, &block)  ⇒ Object 
    Also known as:
    an_object_satisfying, satisfying
    


  

    
Passes if the submitted block returns true. Yields target to the
block.


Generally speaking, this should be thought of as a last resort when
you can't find any other way to specify the behaviour you wish to
specify.


If you do find yourself in such a situation, you could always write
a custom matcher, which would likely make your specs more expressive.

  





  

    
Examples:

      
expect(5).to satisfy { |n| n > 3 }
expect(5).to satisfy("be greater than 3") { |n| n > 3 }

  


Parameters:


    
    
  • 
        description
        (String)
        (defaults to: nil)
        —
        
    optional description to be used for this matcher.
    

    
    
    • 




  

    
      
813
814
815

    		
    
      
# File 'lib/rspec/matchers.rb', line 813
def satisfy(description=nil, &block)
  BuiltIn::Satisfy.new(description, &block)
end

    		
  





      

  

    #start_with(*expected)  ⇒ Object 
    Also known as:
    a_collection_starting_with, a_string_starting_with, starting_with
    


  

    
Matches if the actual value starts with the expected value(s). In the
case of a string, matches against the first expected.length characters
of the actual string. In the case of an array, matches against the first
expected.length elements of the actual array.

  





  

    
Examples:

      
expect("this string").to   start_with "this s"
expect([0, 1, 2, 3, 4]).to start_with 0
expect([0, 2, 3, 4, 4]).to start_with 0, 1

  



  

    
      
828
829
830

    		
    
      
# File 'lib/rspec/matchers.rb', line 828
def start_with(*expected)
  BuiltIn::StartWith.new(*expected)
end

    		
  





      

  

    #throw_symbol(expected_symbol = nil, expected_arg = nil)  ⇒ Object 
    Also known as:
    a_block_throwing, throwing
    


  

    
Given no argument, matches if a proc throws any Symbol.


Given a Symbol, matches if the given proc throws the specified Symbol.


Given a Symbol and an arg, matches if the given proc throws the
specified Symbol with the specified arg.

  





  

    
Examples:

      
expect { do_something_risky }.to throw_symbol
expect { do_something_risky }.to throw_symbol(:that_was_risky)
expect { do_something_risky }.to throw_symbol(:that_was_risky, 'culprit')
expect { do_something_risky }.not_to throw_symbol
expect { do_something_risky }.not_to throw_symbol(:that_was_risky)
expect { do_something_risky }.not_to throw_symbol(:that_was_risky, 'culprit')

  



  

    
      
850
851
852

    		
    
      
# File 'lib/rspec/matchers.rb', line 850
def throw_symbol(expected_symbol=nil, expected_arg=nil)
  BuiltIn::ThrowSymbol.new(expected_symbol, expected_arg)
end

    		
  





      

  

    #yield_control  ⇒ Object 
    Also known as:
    a_block_yielding_control, yielding_control
    


  

  

    Note:
    
Your expect block must accept a parameter and pass it on to
the method-under-test as a block.



  


Passes if the method called in the expect block yields, regardless
of whether or not arguments are yielded.

  





  

    
Examples:

      
expect { |b| 5.tap(&b) }.to yield_control
expect { |b| "a".to_sym(&b) }.not_to yield_control

  



  

    
      
871
872
873

    		
    
      
# File 'lib/rspec/matchers.rb', line 871
def yield_control
  BuiltIn::YieldControl.new
end

    		
  





      

  

    #yield_successive_args(*args)  ⇒ Object 
    Also known as:
    a_block_yielding_successive_args, yielding_successive_args
    


  

  

    Note:
    
Your expect block must accept a parameter and pass it on to
the method-under-test as a block.



  


Designed for use with methods that repeatedly yield (such as
iterators). Passes if the method called in the expect block yields
multiple times with arguments matching those given.


Argument matching is done using === (the case match operator)
and ==. If the expected and actual arguments match with either
operator, the matcher will pass.

  





  

    
Examples:

      
expect { |b| [1, 2, 3].each(&b) }.to yield_successive_args(1, 2, 3)
expect { |b| { :a => 1, :b => 2 }.each(&b) }.to yield_successive_args([:a, 1], [:b, 2])
expect { |b| [1, 2, 3].each(&b) }.not_to yield_successive_args(1, 2)

  



  

    
      
940
941
942

    		
    
      
# File 'lib/rspec/matchers.rb', line 940
def yield_successive_args(*args)
  BuiltIn::YieldSuccessiveArgs.new(*args)
end

    		
  





      

  

    #yield_with_args(*args)  ⇒ Object 
    Also known as:
    a_block_yielding_with_args, yielding_with_args
    


  

  

    Note:
    
Your expect block must accept a parameter and pass it on to
the method-under-test as a block.



  

  

    Note:
    
This matcher is not designed for use with methods that yield
multiple times.



  


Given no arguments, matches if the method called in the expect
block yields with arguments (regardless of what they are or how
many there are).


Given arguments, matches if the method called in the expect block
yields with arguments that match the given arguments.


Argument matching is done using === (the case match operator)
and ==. If the expected and actual arguments match with either
operator, the matcher will pass.

  





  

    
Examples:

      
expect { |b| 5.tap(&b) }.to yield_with_args # because #tap yields an arg
expect { |b| 5.tap(&b) }.to yield_with_args(5) # because 5 == 5
expect { |b| 5.tap(&b) }.to yield_with_args(Integer) # because Integer === 5
expect { |b| File.open("f.txt", &b) }.to yield_with_args(/txt/) # because /txt/ === "f.txt"

expect { |b| User.transaction(&b) }.not_to yield_with_args # because it yields no args
expect { |b| 5.tap(&b) }.not_to yield_with_args(1, 2, 3)

  



  

    
      
919
920
921

    		
    
      
# File 'lib/rspec/matchers.rb', line 919
def yield_with_args(*args)
  BuiltIn::YieldWithArgs.new(*args)
end

    		
  





      

  

    #yield_with_no_args  ⇒ Object 
    Also known as:
    a_block_yielding_with_no_args, yielding_with_no_args
    


  

  

    Note:
    
Your expect block must accept a parameter and pass it on to
the method-under-test as a block.



  

  

    Note:
    
This matcher is not designed for use with methods that yield
multiple times.



  


Passes if the method called in the expect block yields with
no arguments. Fails if it does not yield, or yields with arguments.

  





  

    
Examples:

      
expect { |b| User.transaction(&b) }.to yield_with_no_args
expect { |b| 5.tap(&b) }.not_to yield_with_no_args # because it yields with `5`
expect { |b| "a".to_sym(&b) }.not_to yield_with_no_args # because it does not yield

  



  

    
      
889
890
891

    		
    
      
# File 'lib/rspec/matchers.rb', line 889
def yield_with_no_args
  BuiltIn::YieldWithNoArgs.new
end