In nodejs-logging, the generated unit test has improper sample message:

            const expectedResponse = [
              generateSampleMessage(new protosTYPE_STRING()),
              generateSampleMessage(new protosTYPE_STRING()),
              generateSampleMessage(new protosTYPE_STRING()),
            ];

which takes ENUM as a class to create an object, this is related to the template in util that actually checks if a type is a primitive type or a message, and substitutes the right thing.
ref: googleapis/nodejs-logging#778