runTests(), when specifying a channel, can only grab a stable version or the latest insiders. That's fine, but there isn't an easy way to say, "grab the either stable or insiders based on the version number". For instance, to fix microsoft/vscode-python#20247 we had to do microsoft/vscode-python@133a8e8 which has to look for the -insiders suffix on the version number. But that means that if we want to test against the oldest supported version of VS Code we have to remove that suffix once that insiders version goes stable to make sure we are testing against it. And this trick doesn't work if we were to use a date-based insiders suffix.

So it would be great to have runTests() be able to take the version from package.json and infer that if the version isn't available as stable then it needs VS Code insiders.