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Using filter_run_when_matching

You can configure a conditional filter that only applies if there are any matching examples using config.filter_run_when_matching. This is commonly used for focus filtering:

RSpec.configure do |c|
  c.filter_run_when_matching :focus
end

This configuration allows you to filter to specific examples or groups by tagging them with :focus metadata. When no example or groups are focused (which should be the norm since it's intended to be a temporary change), the filter will be ignored.

RSpec also provides aliases--fit, fdescribe and fcontext--as a shorthand for it, describe and context with :focus metadata, making it easy to temporarily focus an example or group by prefixing an f.

Background​

Given a file named "spec/spec_helper.rb" with:

RSpec.configure do |c|
  c.filter_run_when_matching :focus
end

And a file named ".rspec" with:

--require spec_helper

And a file named "spec/example_spec.rb" with:

RSpec.describe "A group" do
  it "has a passing example" do
  end

  context "a nested group" do
    it "also has a passing example" do
    end
  end
end

The filter is ignored when nothing is focused​

When I run rspec --format doc

Then it should pass with "2 examples, 0 failures"

And the output should contain:

A group
  has a passing example
  a nested group
    also has a passing example

Examples can be focused with fit​

Given I have changed it "has a passing example" to fit "has a passing example" in "spec/example_spec.rb"

When I run rspec --format doc

Then it should pass with "1 example, 0 failures"

And the output should contain:

A group
  has a passing example

Groups can be focused with fdescribe or fcontext​

Given I have changed context to fcontext in "spec/example_spec.rb"

When I run rspec --format doc

Then it should pass with "1 example, 0 failures"

And the output should contain:

A group
  a nested group
    also has a passing example