Mocking runtime config value with sinon

I am adding some config values before hapi server start. Application is works fine although in test I can not use config.get(). I can get around with proxyquire. So I was wondering

• Is adding config file "dynamically" is bad design?
• Is there a way I can use config.get() in such suitation?

• Any alternative approach?

  //initialize.jsconst config = require('config');async function startServe() {  const someConfigVal = await callAPIToGetSomeJSONObject();  config.dynamicValue = someConfigVal;  server.start(); }//doSomething.jsconst config = require('config');function doesWork() {  const valFromConfig = config.dynamicValue.X;  // In test I can use proxiquire by creating config object  ...}function doesNotWork() {  const valFromConfig = config.get('dynamicValue.X');   // Does not work with sinon mocking as this value does not exist in config when test run.  // sinon.stub(config, 'get').withArgs('dynamicValue.X').returns(someVal);  .....}