diff --git a/test/test_jobs_queue.rb b/test/test_jobs_queue.rb
new file mode 100644
index 0000000..136b574
--- /dev/null
+++ b/test/test_jobs_queue.rb
@@ -0,0 +1,187 @@
+require 'minitest/autorun'
+require 'prism'
+require 'tmpdir'
+require 'fileutils'
+
+class JobsQueueTest < Minitest::Test
+  def setup
+    @dir = Dir.mktmpdir('prism-jobs-queue')
+    @queue = Prism::Jobs::Queue.new(File.join(@dir, 'jobs.pstore'))
+  end
+
+  def teardown
+    FileUtils.remove_entry(@dir)
+  end
+
+  def test_enqueue_returns_an_incrementing_id
+    first = @queue.enqueue(job_class: 'X', args: [])
+    second = @queue.enqueue(job_class: 'X', args: [])
+    assert_equal first + 1, second
+  end
+
+  def test_next_ready_returns_the_earliest_due_pending_job
+    later = @queue.enqueue(job_class: 'X', args: [1], run_at: Time.now - 5)
+    sooner = @queue.enqueue(job_class: 'X', args: [2], run_at: Time.now - 50)
+    job = @queue.next_ready
+    assert_equal sooner, job[:id]
+    refute_equal later, job[:id]
+  end
+
+  def test_jobs_scheduled_in_the_future_are_not_ready
+    @queue.enqueue(job_class: 'X', args: [], run_at: Time.now + 3600)
+    assert_nil @queue.next_ready
+  end
+
+  def test_next_ready_respects_queue_name_filter
+    @queue.enqueue(job_class: 'X', args: [], queue_name: 'mailers')
+    critical_id = @queue.enqueue(job_class: 'X', args: [], queue_name: 'critical')
+    job = @queue.next_ready(queue_name: 'critical')
+    assert_equal critical_id, job[:id]
+  end
+
+  def test_claim_next_returns_the_earliest_due_pending_job_and_marks_it_processing
+    later = @queue.enqueue(job_class: 'X', args: [1], run_at: Time.now - 5)
+    sooner = @queue.enqueue(job_class: 'X', args: [2], run_at: Time.now - 50)
+
+    job = @queue.claim_next!
+    assert_equal sooner, job[:id]
+    refute_equal later, job[:id]
+    assert_equal 'processing', job[:status]
+    assert_equal 'processing', @queue.pending_jobs.find { |j| j[:id] == sooner }[:status]
+  end
+
+  def test_claim_next_never_returns_the_same_job_twice
+    id = @queue.enqueue(job_class: 'X', args: [])
+    first = @queue.claim_next!
+    second = @queue.claim_next!
+    assert_equal id, first[:id]
+    assert_nil second
+  end
+
+  def test_claim_next_respects_queue_name_filter
+    @queue.enqueue(job_class: 'X', args: [], queue_name: 'mailers')
+    critical_id = @queue.enqueue(job_class: 'X', args: [], queue_name: 'critical')
+    job = @queue.claim_next!(queue_name: 'critical')
+    assert_equal critical_id, job[:id]
+  end
+
+  def test_claim_next_is_nil_when_nothing_is_ready
+    @queue.enqueue(job_class: 'X', args: [], run_at: Time.now + 3600)
+    assert_nil @queue.claim_next!
+  end
+
+  # Real cross-process race: two OS processes sharing the same PStore file
+  # both try to grab the same batch of jobs at once. #claim_next! selects
+  # and flips status to 'processing' inside one flock'd write transaction,
+  # so the file itself is the arbiter of who wins each job - no job should
+  # ever be claimed by more than one process.
+  def test_claim_next_is_safe_across_real_concurrent_processes
+    queue_path = File.join(@dir, 'jobs.pstore')
+    job_count = 40
+    job_count.times { @queue.enqueue(job_class: 'X', args: []) }
+
+    claims_dir = File.join(@dir, 'claims')
+    FileUtils.mkdir_p(claims_dir)
+    claimer_script = File.join(@dir, 'claimer.rb')
+    File.write(claimer_script, <<~RUBY)
+      require 'prism'
+      queue = Prism::Jobs::Queue.new(#{queue_path.inspect})
+      claims_dir = #{claims_dir.inspect}
+      loop do
+        job = queue.claim_next!
+        break unless job
+        File.write(File.join(claims_dir, "\#{job[:id]}.claim"), Process.pid.to_s)
+      end
+    RUBY
+
+    pids = 4.times.map do
+      Process.spawn(RbConfig.ruby, '-I', File.expand_path('../lib', __dir__), claimer_script,
+                     out: File::NULL, err: File::NULL)
+    end
+    pids.each { |pid| Process.waitpid(pid) }
+
+    claim_files = Dir.glob(File.join(claims_dir, '*.claim'))
+    assert_equal job_count, claim_files.size, 'every enqueued job should have been claimed exactly once'
+    assert_equal claim_files.size, claim_files.map { |f| File.basename(f) }.uniq.size,
+                 'no job id should have produced more than one claim file'
+  end
+
+  def test_mark_completed_removes_the_job
+    id = @queue.enqueue(job_class: 'X', args: [])
+    @queue.mark_completed(id)
+    assert_nil @queue.next_ready
+    assert_equal 0, @queue.size
+  end
+
+  def test_mark_failed_reschedules_with_exponential_backoff_until_max_attempts
+    id = @queue.enqueue(job_class: 'X', args: [], max_attempts: 3, backoff: { strategy: :exponential, base_delay: 2 })
+    before = Time.now
+    @queue.mark_failed(id, 'boom')
+    job = @queue.pending_jobs.first
+    assert_equal 1, job[:attempts]
+    assert_equal 'pending', job[:status]
+    assert_equal 'boom', job[:last_error]
+    assert_in_delta (before + 2).to_f, job[:run_at].to_f, 1.0
+
+    @queue.mark_failed(id, 'boom again')
+    job = @queue.pending_jobs.first
+    assert_equal 2, job[:attempts]
+    assert_in_delta (before + 4).to_f, job[:run_at].to_f, 1.0
+  end
+
+  def test_mark_failed_dead_letters_after_exhausting_max_attempts
+    id = @queue.enqueue(job_class: 'X', args: [], max_attempts: 2)
+    @queue.mark_failed(id, 'first failure')
+    @queue.mark_failed(id, 'second failure')
+
+    assert_equal 0, @queue.size
+    assert_equal 1, @queue.dead_letter_size
+    dead = @queue.dead_jobs.first
+    assert_equal 'dead', dead[:status]
+    assert_equal 'second failure', dead[:last_error]
+  end
+
+  def test_retry_dead_moves_a_dead_job_back_to_pending
+    id = @queue.enqueue(job_class: 'X', args: [], max_attempts: 1)
+    @queue.mark_failed(id, 'fatal')
+    assert_equal 1, @queue.dead_letter_size
+
+    @queue.retry_dead(id)
+    assert_equal 0, @queue.dead_letter_size
+    job = @queue.next_ready
+    assert_equal id, job[:id]
+    assert_equal 0, job[:attempts]
+    assert_nil job[:last_error]
+  end
+
+  def test_linear_backoff_grows_by_a_constant_step
+    id = @queue.enqueue(job_class: 'X', args: [], max_attempts: 5, backoff: { strategy: :linear, base_delay: 3 })
+    before = Time.now
+    @queue.mark_failed(id, 'e1')
+    job = @queue.pending_jobs.first
+    assert_in_delta (before + 3).to_f, job[:run_at].to_f, 1.0
+
+    @queue.mark_failed(id, 'e2')
+    job = @queue.pending_jobs.first
+    assert_in_delta (before + 6).to_f, job[:run_at].to_f, 1.0
+  end
+
+  def test_state_survives_reopening_the_store
+    id = @queue.enqueue(job_class: 'PersistedJob', args: [42])
+    path = File.join(@dir, 'jobs.pstore')
+    reopened = Prism::Jobs::Queue.new(path)
+    job = reopened.next_ready
+    assert_equal id, job[:id]
+    assert_equal [42], job[:args]
+  end
+
+  def test_clear_empties_both_tables
+    @queue.enqueue(job_class: 'X', args: [])
+    dead_id = @queue.enqueue(job_class: 'X', args: [], max_attempts: 1)
+    @queue.mark_failed(dead_id, 'boom')
+
+    @queue.clear!
+    assert_equal 0, @queue.size
+    assert_equal 0, @queue.dead_letter_size
+  end
+end