/usr/share/doc/ruby-rspec-mocks/features/verifying_doubles/instance_doubles.feature is in ruby-rspec-mocks 3.4.0c3e0m1s1-1ubuntu1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 | Feature: Using an instance double
An `instance_double` is the most common type of verifying double. It takes a class name or
object as its first argument, then verifies that any methods being stubbed would be present
on an _instance_ of that class. In addition, when it receives messages, it verifies that the
provided arguments are supported by the method signature, both in terms of arity and
allowed or required keyword arguments, if any. The same argument verification happens
when you [constrain the arguments](../setting-constraints/matching-arguments) using `with`.
For methods handled by `method_missing`, see [dynamic classes](./dynamic-classes).
Background:
Given a file named "app/models/user.rb" with:
"""ruby
class User < Struct.new(:notifier)
def suspend!
notifier.notify("suspended as")
end
end
"""
Given a file named "spec/unit_helper.rb" with:
"""ruby
$LOAD_PATH.unshift("app/models")
"""
Given a file named "spec/spec_helper.rb" with:
"""ruby
require 'unit_helper'
require 'user'
require 'console_notifier'
RSpec.configure do |config|
config.mock_with :rspec do |mocks|
# This option should be set when all dependencies are being loaded
# before a spec run, as is the case in a typical spec helper. It will
# cause any verifying double instantiation for a class that does not
# exist to raise, protecting against incorrectly spelt names.
mocks.verify_doubled_constant_names = true
end
end
"""
Given a file named "spec/unit/user_spec.rb" with:
"""ruby
require 'unit_helper'
require 'user'
RSpec.describe User, '#suspend!' do
it 'notifies the console' do
notifier = instance_double("ConsoleNotifier")
expect(notifier).to receive(:notify).with("suspended as")
user = User.new(notifier)
user.suspend!
end
end
"""
Scenario: spec passes in isolation
When I run `rspec spec/unit/user_spec.rb`
Then the examples should all pass
Scenario: spec passes with dependencies loaded and method implemented
Given a file named "app/models/console_notifier.rb" with:
"""ruby
class ConsoleNotifier
def notify(msg)
puts message
end
end
"""
When I run `rspec -r./spec/spec_helper spec/unit/user_spec.rb`
Then the examples should all pass
Scenario: spec fails with dependencies loaded and method unimplemented
Given a file named "app/models/console_notifier.rb" with:
"""ruby
class ConsoleNotifier
end
"""
When I run `rspec -r./spec/spec_helper spec/unit/user_spec.rb`
Then the output should contain "1 example, 1 failure"
And the output should contain "ConsoleNotifier class does not implement the instance method:"
Scenario: spec fails with dependencies loaded and incorrect arity
Given a file named "app/models/console_notifier.rb" with:
"""ruby
class ConsoleNotifier
def notify(msg, color)
puts color + message
end
end
"""
When I run `rspec -r./spec/spec_helper spec/unit/user_spec.rb`
Then the output should contain "1 example, 1 failure"
And the output should contain "Wrong number of arguments."
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