add docs

README.md

@@ -99,7 +99,7 @@ expect(AwesomeJob).to have_enqueued_sidekiq_job(hash_excluding("bad_stuff" => an
 
 #### Testing scheduled jobs
 
-*Use chainable matchers `#at` and `#in`*
+*Use chainable matchers `#at`, `#in` and `#immediately`*
 
 ```ruby
 time = 5.minutes.from_now
@@ -113,6 +113,13 @@ AwesomeJob.perform_in 5.minutes, 'Awesome', true
 expect(AwesomeJob).to have_enqueued_sidekiq_job('Awesome', true).in(5.minutes)
 ```
 
+```ruby
+# Job scheduled for a date in the past are enqueued immediately.
+AwesomeJob.perform_later 5.minutes.ago, 'Awesome', true # equivalent to: AwesomeJob.perform_async 'Awesome', true
+# test with...
+expect(AwesomeJob).to have_enqueued_sidekiq_job('Awesome', true).immediately
+```
+
 #### Testing queue set for job
 
 Use the chainable `#on` matcher

lib/rspec/sidekiq/matchers/enqueue_sidekiq_job.rb

@@ -56,7 +56,7 @@ def supports_block_expectations?
       #
       # Passes if a Job is enqueued as the result of a block. Chainable `with`
       # for arguments, `on` for queue, `at` for queued for a specific time, and
-      # `in` for a specific interval delay to being queued
+      # `in` for a specific interval delay to being queued, `immediately` for queued without delay.
       #
       # @example
       #
@@ -79,6 +79,11 @@ def supports_block_expectations?
       #   freeze_time do
       #     expect { AwesomeJob.perform_in(1.hour) }.to enqueue_sidekiq_job.in(1.hour)
       #   end
+      #
+      #   # Without any delay
+      #   expect { AwesomeJob.perform_async }.to enqueue_sidekiq_job.immediately
+      #   expect { AwesomeJob.perform_at(1.hour.ago) }.to enqueue_sidekiq_job.immediately
+
       def enqueue_sidekiq_job(job_class = nil)
         EnqueueSidekiqJob.new(job_class)
       end