mocks

General purpose mocking library for Crystal.

Installation

Add it to shard.yml:

dependencies:
  mocks:
    github: waterlink/mocks.cr
    version: ~> 0.9

This shard requires version of Crystal minimum 0.13.0.

Usage

require "mocks"

Usage with spec library

require "mocks/spec"

This will automatically register Mocks.reset hooks in before_each and after_each. Additionally it makes allow, receive and have_received available in global scope.

If you need all of macros (such as: create_mock, create_double, double, instance_double, etc.) to be available in global scope use include ::Mocks::Macro.

Usage with spec2 library

First add spec2-mocks to your dependencies:

dependencies:
  mocks:
    github: waterlink/mocks.cr
  spec2:
    github: waterlink/spec2.cr
  spec2-mocks:
    github: waterlink/spec2-mocks.cr

Run crystal deps update and do:

require "spec2-mocks"

This should be enough to start using mocks together with spec2.

Partial double

class Example
  def say_hello(name)
    "hey, #{name}"
  end
end

Mocks.create_mock Example do
  mock say_hello(name)
  # or
  # mock instance.say_hello(name)
end

example = Example.new
allow(example).to receive(say_hello("world")).and_return("hello, world!")

example.say_hello("world")    #=> "hello, world!"
example.say_hello("john")     #=> "hey, john"

If you want to mock operators or setters, syntax is pretty straightforward:

# setter
mock instance.greeting = value
# or
mock instance.greeting=(value)

# equals
mock instance == other
# or
mock instance.==(other)

Class methods

Just use mock self.method_name(args..)

Mocks.create_mock Example do
  mock self.hello_world(greeting)
end

allow(Example).to receive(self.hello_world("aloha")).and_return("aloha (as 'hello'), world!")
Example.hello_world("hey")         # => "hey, world!"                   (original was called)
Example.hello_world("aloha")       # => "aloha (as 'hello'), world!"    (mock was called)

Module methods

Just use mock self.method_name(args..)

module Example
  def self.hello_world(greeting)
    greeting
  end
end

Mocks.create_module_mock Example do
  mock self.hello_world(greeting)
end

allow(Example).to receive(self.hello_world("aloha")).and_return("aloha (as 'hello'), world!")

Mocking Struct

struct Example
  def now
    Time.now
  end
end

Mocks.create_struct_mock Example do
  mock now
end

example = Example.new
allow(example).to receive(now).and_return(Time.new(2014, 12, 22))

Double

Caution: doubles require return types.

Mocks.create_double "OtherExample" do
  mock say_hello(name).as(String)
  mock greetings_count.as(Int64)

  # For setters and operators this is the only syntax allowed:
  # ( parenthesis are mandatory not to confuse Crystal's parser )
  mock (instance.greeting = value), String
  mock (instance == other), Bool
end

example = Mocks.double("OtherExample", returns(say_hello("world"), "hello world!"))
allow(example).to receive(instance.greeting=("hey")).and_return("hey")

example.say_hello("world")     #=> "hello world!"
example.say_hello("john")      #=> Mocks::UnexpectedMethodCall: #<Mocks::Doubles::OtherExample:0x109498F00> received unexpected method call say_hello["john"]

Instance double

After defining Example's mock with create_mock you can use it as an instance_double:

example = Mocks.instance_double(Example, returns(say_hello("world"), "hello, world!"))
allow(example).to receive(say_hello("sarah")).and_return("Hey, Sarah!")

example.say_hello("world")     #=> "hello world!"
example.say_hello("sarah")     #=> "Hey, Sarah!"
example.say_hello("john")      #=> Mocks::UnexpectedMethodCall: #<Mocks::InstanceDoubles::Example:0x109498F00> received unexpected method call say_hello["john"]

Class double

After defining Example's mock with create_mock you can use it as a class_double:

example_class = Mocks.class_double(Example, returns(self.hello_world("aloha"), "aloha, world!"))
allow(example_class).to receive(self.hello_world("hi")).and_return("hey, world!")

example_class.hello_world("aloha")            # => "aloha, world!"
example_class.hello_world("hi")               # => "hey, world!"
example_class.hello_world("halo")             # => Mocks::UnexpectedMethodCall: Mocks::InstanceDoubles::Example received unexpected method call self.hello_world["halo"]

.new

It returns normal instance_double:

example_class = Mocks.class_double(Example)
example_class.new          # => #<Mocks::InstanceDoubles::Example:0x109498F00>

HaveReceived expectation (usage with stdlib spec)

example = Example.new
example.say("hello")
example.should have_received(say("hello"))   # passes
example.should have_received(say("hi"))      # fails

Development

After cloning the project:

cd mocks.cr
crystal deps   # install dependencies
crystal spec   # run specs

Just use normal TDD development style.

Contributing

1. Fork it ( https://github.com/waterlink/mocks.cr/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• waterlink Oleksii Fedorov - creator, maintainer