Stub logging and add stdout logging spec

Suppress the RSpec/AnyInstance cop to allow stubbing of described_class#log_internal_error in the middleware spec (TODO: remove later). Add a new example that asserts an unexpected JSON-RPC internal error is logged to stdout, ensuring the middleware both returns the correct error response and emits an internal error message.

Author: wilsonsilva

spec/jsonrpc/middleware_spec.rb

@@ -390,6 +390,11 @@
 
   context 'when processing a JSON-RPC request that causes an unexpected exception' do
     it 'returns HTTP 200 OK with a JSON-RPC internal error' do
+      # TODO: Remove this in the next iteration
+      # rubocop:disable RSpec/AnyInstance
+      allow_any_instance_of(described_class).to receive(:log_internal_error)
+      # rubocop:enable RSpec/AnyInstance
+
       post_jsonrpc_request(
         jsonrpc: '2.0',
         method: 'explode',
@@ -407,6 +412,16 @@
         id: 'req-internal-error'
       )
     end
+
+    it 'logs the internal error to stdout' do
+      expect do
+        post_jsonrpc_request(
+          jsonrpc: '2.0',
+          method: 'explode',
+          id: 'req-internal-error'
+        )
+      end.to output(/Internal error: Internal JSON-RPC error\./).to_stdout
+    end
   end
 
   # Batch Requests