Added not on how to see Oj in traces.
@@ -87,3 +87,7 @@ Oj::Rails.set_decoder() method replaces that method with the Oj equivelant.
that has already been used. This could occur is a mix of String and Symbols
are used as keys or if a other non-String objects such as Numerics are mixed
with numbers as Strings.
+
+3. To verify Oj is being used turn on trace and then set the
+ `Tracer.display_c_call = true` to see calls to C extensions.
+
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