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Project: RSpec Mocks 2.14

Publisher: RSpec

expect message using `expect`

Use expect(object).to receive(:message) to set an expectation that
object should receive the message :message before the example is
completed.

Note: You can use expect_any_instance_of when you don't have a reference
to the object that receives a message in your test. For more information,
see the message_expectations/expect_any_instance_of feature.

Scenarios
  1. expect a message
  2. expect a message with an argument
  3. provide a return value
  4. expect a specific number of calls
expect a message
Given
a file named "spec/account_spec.rb" with: 
require "account"

describe Account do
  context "when closed" do
    it "logs an account closed message" do
      logger = double("logger")
      account = Account.new logger

      expect(logger).to receive(:account_closed)

      account.close
    end
  end
end
And
a file named "lib/account.rb" with: 
Account = Struct.new(:logger) do
  def close
    logger.account_closed
  end
end
When
I run rspec spec/account_spec.rb
Then
the output should contain "1 example, 0 failures"
expect a message with an argument
Given
a file named "spec/account_spec.rb" with: 
require "account"

describe Account do
  context "when closed" do
    it "logs an account closed message" do
      logger = double("logger")
      account = Account.new logger

      expect(logger).to receive(:account_closed).with(account)

      account.close
    end
  end
end
And
a file named "lib/account.rb" with: 
Account = Struct.new(:logger) do
  def close
    logger.account_closed(self)
  end
end
When
I run rspec spec/account_spec.rb
Then
the output should contain "1 example, 0 failures"
provide a return value
Given
a file named "spec/message_expectation_spec.rb" with: 

describe "a message expectation with a return value" do
  context "specified in a block" do
    it "returns the specified value" do
      object = double("object")
      expect(object).to receive(:message) { :return_value }
      object.message.should eq(:return_value)
    end
  end

  context "specified with and_return" do
    it "returns the specified value" do
      object = double("object")
      expect(object).to receive(:message).and_return(:return_value)
      object.message.should eq(:return_value)
    end
  end
end
When
I run rspec spec/message_expectation_spec.rb
Then
the output should contain "2 examples, 0 failures"
expect a specific number of calls
Given
a file named "spec/message_count_spec.rb" with: 
describe "a message expectation with a count" do
  it "passes if the expected number of calls happen" do
    string = "hi"
    expect(string).to receive(:length).exactly(3).times

    3.times { string.length }
  end
end
When
I run rspec spec/message_count_spec.rb
Then
the output should contain "1 example, 0 failures"

Last published about 7 years ago by myronmarston.