Authorization header isn't mocked. package: node-mocks-http

Question

**Note:** My test case is running successfully but the issue is it is not mocking the header. 
   

describe('Collection Listing API', () => {
      let req;
      let res;
      let sandbox;
      const token = 'string';
      before(() => {
        req = httpMocks.createRequest({
          method: 'GET',
          url: '/data/collections',
          params: {
            cusId: data.customerId,
          },
          headers: { Authorization: `Bearer ${token}` },
        });
    
        res = httpMocks.createResponse();
        
      });
    
      it.only('should return true for valid collection ', async () => {
       //testcase
      });

    });

i want to check the header token also. I just import the controller function and calling it inside test case and inside before i'm mocking the request but header is not mocked.