This test is failing on macOS:

https://github.com/Microsoft/vscode-python/blob/3cd69454e55fdc2bbe73fe0b585d689ff03808d1/src/test/common/utils/cacheUtils.unit.test.ts#L107

For the scenario of 'simple string' and 'undefined'.
Both are failing after only waiting for 50ms (they should make it until after 100ms).

Investigate (on Mac) and correct.