Move test into separate file

This test was failing on Travis when run in parallel with other tests in
the TestIntegrationCluster test. Removing the line "parallelize_me!"
from the top of the file worked, but I chose to move the test into its own
file to keep the existing tests running in parallel.

test/test_integration_cluster.rb

@@ -133,30 +133,6 @@ class TestIntegrationCluster < TestIntegration
     worker_respawn { |phase0_worker_pids| Process.kill :USR1, @pid }
   end
 
-  # It does not wipe out BUNDLE_GEMFILE et al
-  def test_usr2_restart_preserves_bundler_environment
-    @tcp_port = UniquePort.call
-    env = {
-      # Intentionally set this to something we wish to keep intact on restarts
-      "BUNDLE_GEMFILE" => "Gemfile.bundle_env_preservation_test",
-      # Don't allow our (rake test's) original env to interfere with the child process
-      "BUNDLER_ORIG_BUNDLE_GEMFILE" => nil
-    }
-    # Must use `bundle exec puma` here, because otherwise Bundler may not be defined, which is required to trigger the bug
-    cmd = "bundle exec puma -q -w 1 --prune-bundler -b tcp://#{HOST}:#{@tcp_port}"
-    Dir.chdir(File.expand_path("bundle_preservation_test", __dir__)) do
-      @server = IO.popen(env, cmd.split, "r")
-    end
-    wait_for_server_to_boot
-    @pid = @server.pid
-    connection = connect
-    initial_reply = read_body(connection)
-    assert_match("Gemfile.bundle_env_preservation_test", initial_reply)
-    restart_server connection
-    new_reply = read_body(connection)
-    assert_match("Gemfile.bundle_env_preservation_test", new_reply)
-  end
-
   private
 
   # Send requests 10 per second.  Send 10, then :TERM server, then send another 30.

test/test_preserve_bundler_env.rb

@@ -0,0 +1,33 @@
+require_relative "helper"
+require_relative "helpers/integration"
+
+class TestPreserveBundlerEnv < TestIntegration
+  def setup
+    skip NO_FORK_MSG unless HAS_FORK
+    super
+  end
+
+  # It does not wipe out BUNDLE_GEMFILE et al
+  def test_usr2_restart_preserves_bundler_environment
+    @tcp_port = UniquePort.call
+    env = {
+      # Intentionally set this to something we wish to keep intact on restarts
+      "BUNDLE_GEMFILE" => "Gemfile.bundle_env_preservation_test",
+      # Don't allow our (rake test's) original env to interfere with the child process
+      "BUNDLER_ORIG_BUNDLE_GEMFILE" => nil
+    }
+    # Must use `bundle exec puma` here, because otherwise Bundler may not be defined, which is required to trigger the bug
+    cmd = "bundle exec puma -q -w 1 --prune-bundler -b tcp://#{HOST}:#{@tcp_port}"
+    Dir.chdir(File.expand_path("bundle_preservation_test", __dir__)) do
+      @server = IO.popen(env, cmd.split, "r")
+    end
+    wait_for_server_to_boot
+    @pid = @server.pid
+    connection = connect
+    initial_reply = read_body(connection)
+    assert_match("Gemfile.bundle_env_preservation_test", initial_reply)
+    restart_server connection
+    new_reply = read_body(connection)
+    assert_match("Gemfile.bundle_env_preservation_test", new_reply)
+  end
+end