ci: remove reference to mock object after test

[Watson1978]

Which issue(s) this PR fixes:
Fixes #5054

What this PR does / why we need it:
This PR will resolve CI error.

Docs Changes:
N/A

Release Note:
N/A

[kenhys]

@Watson1978

Could you add reference to #5054 in commit message?

Except above, LGTM.

[daipom]

Thanks for this fix!
Even with this fix, the test still sometimes fails on my local environment.
Looks like we need the following points.

• We should do GC.start for ObjectSpaceInputTest to ensure GC.
• Fluent::Test.setup must ensure the initialization of Fluent::Engine.
  • It is very strange, but even if we do both remove_const and GC.start, some objects can still exist. So, it appears that we need to set nil explicitly, as your fix.

For example, how about the following fix?

diff --git a/lib/fluent/test.rb b/lib/fluent/test.rb
index ed2c3a26..6a08d5d8 100644
--- a/lib/fluent/test.rb
+++ b/lib/fluent/test.rb
@@ -40,7 +40,11 @@ module Fluent
 
       $log = dummy_logger
 
-      Fluent.__send__(:remove_const, :Engine)
+      old_engine = Fluent.__send__(:remove_const, :Engine)
+      # Ensure that GC can remove the objects of the old engine.
+      # Some objects can still exist after `remove_const`. See https://github.com/fluent/fluentd/pull/5055.
+      old_engine.instance_variable_set(:@root_agent, nil)
+
       engine = Fluent.const_set(:Engine, EngineClass.new).init(SystemConfig.new)
 
       engine.define_singleton_method(:now=) {|n|
diff --git a/test/plugin/test_in_object_space.rb b/test/plugin/test_in_object_space.rb
index 6e8bfa52..e734f398 100644
--- a/test/plugin/test_in_object_space.rb
+++ b/test/plugin/test_in_object_space.rb
@@ -21,6 +21,7 @@ class ObjectSpaceInputTest < Test::Unit::TestCase
 
   def setup
     Fluent::Test.setup
+    GC.start
     # Overriding this behavior in the global scope will have an unexpected influence on other tests.
     # So this should be overridden here and be removed in `teardown`.
     def FailObject.class

[Watson1978]

hmm, I approve to add GC.start, but I wonder if we need remove_const...

[Watson1978]

Could you add reference to #5054 in commit message?

Added in 4ef10d2

[daipom]

hmm, I approve to add GC.start, but I wonder if we need remove_const...

remove_const is the original code of Fluent::Test.setup.

fluentd/lib/fluent/test.rb

Lines 43 to 44 in fd711c5

	Fluent.__send__(:remove_const, :Engine)
	engine = Fluent.const_set(:Engine, EngineClass.new).init(SystemConfig.new)

What I want to say is that each test should not consider the initialization of Fluent::Engine.
It should be the responsibility of Fluent::Test.setup.

[Watson1978]

What I want to say is that each test should not consider the initialization of Fluent::Engine.
It should be the responsibility of Fluent::Test.setup.

Hmmm, sounds it is not related to this PR.

[daipom]

What I want to say is that each test should not consider the initialization of Fluent::Engine.
It should be the responsibility of Fluent::Test.setup.

Hmmm, sounds it is not related to this PR.

OK. Let's separate the PRs.
I will send the PR later.

[daipom]

LGTM! Thanks!

[kenhys]

LGTM.