add regression test for #1639

added a regression test for #1639 that reproduces the issue of being
unable to call `(self.)client.db` when `(self.)client` returns an
instance of `RedisClient` and not `Redis::Client`

.rubocop.yml

@@ -1331,13 +1331,15 @@ Style/MethodCallWithArgsParentheses:
     - add_development_dependency
     - expect
     - fail
+    - gem
     - include
     - print
     - puts
     - pp
     - raise
     - require
     - skip
+    - source
     - stub
   AllowedPatterns: [^assert, ^refute]
 

sidekiq_with_redis_test.rb

@@ -0,0 +1,72 @@
+# This file is distributed under New Relic's license terms.
+# See https://github.com/newrelic/newrelic-ruby-agent/blob/main/LICENSE for complete details.
+# frozen_string_literal: true
+
+require 'bundler/inline'
+
+class SidekiqWithRedisTest < MiniTest::Test
+  #
+  # Regression test for
+  #   https://github.com/newrelic/newrelic-ruby-agent/issues/1639
+  #
+  # PR 1611 introduced a new `call_pipelined_with_tracing` method to
+  # `lib/new_relic/agent/instrumentation/redis/instrumentation.rb`. That method
+  # is defined on all instrumented instances of RedisClient (defined by the
+  # `redis-client` gem) when v5.0+ of the `redis` gem (which requires
+  # `redis-client`) is used. Originally the new method performed a
+  # `client.db` call on `self` to get at the client's configured database value.
+  # At the time, `client` was assumed to always return an instance of
+  # `Redis::Client` which is a class defined by the `redis` gem. This
+  # `Redis::Client` class has a `db` helper method that exposes the configured
+  # database value.
+  #
+  # With Issue 1639 it was discovered that `client` could return an instance
+  # of `RedisClient` (defined by the `redis-client` gem) instead of
+  # `Redis::Client` (defined by the `redis` gem). The original `client.db` call
+  # was updated to read `client.config.db` instead. This approach is known to
+  # work for instances of `RedisClient` and `Redis::Client`, as
+  # `Redis::Client#db` is just a helper method that calls `config.db`.
+  #
+  # This test reproduces the problem by placing an instance of `RedisClient` in
+  # scope when the `call_pipelined_with_tracing` method calls `client`, and
+  # confirms that the instrumentation no longer (and never again) errors out.
+  #
+  # NOTE: Because Sidekiq v7.0+ can use `redis-client` without `redis`, this
+  #       test brings in the `redis` gem directly via `bundler/inline`
+  def test_redis_client_pipelined_calls_work
+    skip unless run_these_tests?
+
+    gemfile do
+      source 'https://rubygems.org'
+
+      gem 'redis'
+    end
+
+    require 'sidekiq'
+    require 'newrelic_rpm'
+
+    conn = Sidekiq::RedisConnection.create
+    key = 'pineapple'
+    value = 'carrot'
+    result = nil
+
+    conn.with do |c|
+      c._client.pipelined do |p|
+        p.call_v([:set, key, value])
+      end
+      result = c._client.call(:get, key)
+    end
+
+    assert_equal value, result
+  end
+
+  private
+
+  def run_these_tests?
+    # these tests aren't impacted by Ruby version
+    return false unless RUBY_VERSION >= '3.1.2'
+
+    # only test with environments that have not already bundled the redis gem
+    !Gem::Specification.all.any? { |s| s.name == 'redis' }
+  end
+end