rabbit_feature_flags:on_load/1: EUnit test env compatibility

rabbit.feature_flags_file would not be set in an EUnit test
environment, so proceed with code loading if eunit is loaded.

References #2133.

1 files changed, 12 insertions, 5 deletions

diff --git a/src/rabbit_feature_flags.erl b/src/rabbit_feature_flags.erl
index 9591cd691d..066a3db0a4 100644
--- a/src/rabbit_feature_flags.erl
+++ b/src/rabbit_feature_flags.erl
@@ -2269,13 +2269,20 @@ share_new_feature_flags_after_app_load(FeatureFlags, Timeout) ->
       node(), FeatureFlags, Timeout).
 
 on_load() ->
+    Vsn = rabbit_data_coercion:to_list(rabbit_misc:version()),
     case application:get_env(rabbit, feature_flags_file) of
         {ok, _} ->
             ok;
         _ ->
-            "Refusing to load '" ?MODULE_STRING "' in what appears to "
-            "be a pre-feature-flags running node "
-            "(" ++ rabbit_misc:version() ++ "). This is fine: it is "
-            "probably a remote node querying this node for its feature "
-            "flags."
+            %% rabbit.feature_flags_file would not be set in unit tests. MK.
+            case code:is_loaded(eunit) of
+              false ->
+                "Refusing to load '" ?MODULE_STRING "' in what appears to "
+                "be a pre-feature-flags running node "
+                "(" ++ Vsn ++ "). This is fine: it is "
+                "probably a remote node querying this node for its feature "
+                "flags.";
+              {file, _} -> ok;
+              _         -> ok
+            end
     end.