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Project: RSpec Expectations 3.6

Publisher: RSpec

Syntax Configuration

  • @allow-disallowed-api

The primary syntax provided by rspec-expectations is based on
the expect method, which explicitly wraps an object or block
of code in order to set an expectation on it.

There's also an older should-based syntax, which relies upon should being
monkey-patched onto every object in the system. However, this syntax can at times lead to
some surprising failures, since RSpec does not own every object in the system and cannot
guarantee that it will always work consistently.

We recommend you use the expect syntax unless you have a specific reason you prefer the
should syntax. We have no plans to ever completely remove the should syntax but starting
in RSpec 3, a deprecation warning will be issued if you do not explicitly enable it, with the
plan to disable it by default in RSpec 4 (and potentially move it into an external gem).

If you have an old should-based project that you would like to upgrade to the expect,
check out transpec, which can perform the conversion automatically for you.

Background
Given
a file named "spec/syntaxes_spec.rb" with: 
require 'spec_helper'

RSpec.describe "using the should syntax" do
  specify { 3.should eq(3) }
  specify { 3.should_not eq(4) }
  specify { lambda { raise "boom" }.should raise_error("boom") }
  specify { lambda { }.should_not raise_error }
end

RSpec.describe "using the expect syntax" do
  specify { expect(3).to eq(3) }
  specify { expect(3).not_to eq(4) }
  specify { expect { raise "boom" }.to raise_error("boom") }
  specify { expect { }.not_to raise_error }
end
Scenarios
  1. Both syntaxes are available by default
  2. Disable should syntax
  3. Disable expect syntax
  4. Explicitly enable both syntaxes
Both syntaxes are available by default
Given
a file named "spec/spec_helper.rb" with:
When
I run rspec
Then
the examples should all pass
And
the output should contain "Using should from rspec-expectations' old :should syntax without explicitly enabling the syntax is deprecated"
Disable should syntax
Given
a file named "spec/spec_helper.rb" with: 
RSpec.configure do |config|
  config.expect_with :rspec do |c|
    c.syntax = :expect
  end
end
When
I run rspec
Then
the output should contain all of these:
8 examples, 4 failures
undefined method `should'
Disable expect syntax
Given
a file named "spec/spec_helper.rb" with: 
RSpec.configure do |config|
  config.expect_with :rspec do |c|
    c.syntax = :should
  end
  config.mock_with :rspec do |c|
    c.syntax = :should
  end
end
When
I run rspec
Then
the output should contain all of these:
8 examples, 4 failures
undefined method `expect'
Explicitly enable both syntaxes
Given
a file named "spec/spec_helper.rb" with: 
RSpec.configure do |config|
  config.expect_with :rspec do |c|
    c.syntax = [:should, :expect]
  end
end
When
I run rspec
Then
the examples should all pass
And
the output should not contain "deprecated"

Last published about 3 years ago by myronmarston.