Add unit tests and deprecation warning for close_on_fork

* Re-add close on fork, but now it emits a deprecation warning
* Add unit tests for ConnectionManager to confirm deprecation warning

Author: PatrickTulskie

lib/dalli/protocol/connection_manager.rb

@@ -226,6 +226,16 @@ def reconnect_on_fork
         establish_connection
       end
 
+      def close_on_fork
+        Dalli.logger.warn 'DEPRECATED: close_on_fork is deprecated and will be removed in a future version. Use reconnect_on_fork instead.'
+        message = 'Fork detected, re-connecting child process...'
+        Dalli.logger.info { message }
+        # Close socket on a fork, setting us up for reconnect
+        # on next request.
+        close
+        raise Dalli::NetworkError, message
+      end
+
       def fork_detected?
         @pid && @pid != PIDCache.pid
       end

test/protocol/test_connection_manager.rb

@@ -0,0 +1,76 @@
+# frozen_string_literal: true
+
+require_relative '../helper'
+
+describe Dalli::Protocol::ConnectionManager do
+  let(:hostname) { 'localhost' }
+  let(:port) { 11_211 }
+  let(:socket_type) { :tcp }
+  let(:client_options) { {} }
+  let(:connection_manager) { Dalli::Protocol::ConnectionManager.new(hostname, port, socket_type, client_options) }
+
+  describe '#close_on_fork' do
+    it 'emits a deprecation warning' do
+      logger_mock = Minitest::Mock.new
+      expected_message = 'DEPRECATED: close_on_fork is deprecated and will be removed in a future version. Use reconnect_on_fork instead.'
+      logger_mock.expect(:warn, nil, [expected_message])
+      logger_mock.expect(:info, nil) { true }
+
+      Dalli.stub(:logger, logger_mock) do
+        assert_raises(Dalli::NetworkError) do
+          connection_manager.close_on_fork
+        end
+      end
+
+      logger_mock.verify
+    end
+
+    it 'raises a NetworkError with the fork detection message' do
+      with_nil_logger do
+        error = assert_raises(Dalli::NetworkError) do
+          connection_manager.close_on_fork
+        end
+        assert_equal 'Fork detected, re-connecting child process...', error.message
+      end
+    end
+
+    it 'closes the socket' do
+      socket_mock = Minitest::Mock.new
+      socket_mock.expect(:close, nil)
+
+      connection_manager.instance_variable_set(:@sock, socket_mock)
+
+      with_nil_logger do
+        assert_raises(Dalli::NetworkError) do
+          connection_manager.close_on_fork
+        end
+      end
+
+      socket_mock.verify
+
+      assert_nil connection_manager.sock
+    end
+  end
+
+  describe '#reconnect_on_fork' do
+    it 'establishes a new connection after closing the old one' do
+      socket_mock = Minitest::Mock.new
+      socket_mock.expect(:close, nil)
+
+      new_socket = Object.new
+
+      connection_manager.instance_variable_set(:@sock, socket_mock)
+      connection_manager.define_singleton_method(:establish_connection) do
+        @sock = new_socket
+      end
+
+      with_nil_logger do
+        connection_manager.reconnect_on_fork
+      end
+
+      socket_mock.verify
+
+      assert_equal new_socket, connection_manager.sock
+    end
+  end
+end