Test two different npm package versions at the same time

When I create an npm package, sometimes it would face the need to backward old dependency package version.

If the new version has new api, I may write the code in this pattern:

import pkg from 'some-pkg';
const isNewVersion = pkg.newVersionApi !== 'undefined';

if (isNewversion) {
  pkg.newVersionApi();
} else {
  pkg.oldVersionApi(); // backward compatible api
}

And with this pattern, when I want to write the test, I only can test the installed version code. The other version's code can't be tested.

For real example, in React v15 and v16, React v16 has new API Portal. Before Portal release, v15 has unstable_renderSubtreeIntoContainer api to realize similar feature.

So the code for React would be like:

import ReactDOM from 'react-dom';
const isV16 = ReactDOM.createPortal !== 'undefined';

if (isV16) {
  ReactDOM.createPortal(...);
} else {
  ReactDOM.unstable_renderSubtreeIntoContainer(...);
}

So I want to ask is there any method to test with different dependency version?

Currently, one method I think of is to install the other version again and test it. But it only can do on local. It can't work on ci and it can't count in coverage together.

I think that is not only for react test. It may face on node.js test. Any suggestion can be discussed.