Disabled backup service in extension tests can cause issues

[jrieken]

See https://github.com/Microsoft/vscode/blob/c93d5e7d9200d4839bd8718c39b577568ab3d78a/extensions/vscode-api-tests/src/singlefolder-tests/workspace.test.ts#L556. The test fails because the document just contains AFTER not AFTERBEFORE

[bpasero]

@jrieken this is because in order to preserve the contents of a model when renaming, I go through our backup service which happens to be disabled when running in a test environment. Once I remove this check for extensions, the test runs green:

https://github.com/Microsoft/vscode/blob/8be8f654687341db407086c7e277d80b7055e12a/src/vs/code/electron-main/windows.ts#L1141-L1149

[jrieken]

@bpasero Is that backupPath something we can simply set to a temp-directory when running like this? Now, almost every extension test I wrote for the workspace edit is partially commented out which doesn't increase my confidence ;-)

[bpasero]

@jrieken yeah I can look into providing a test-implementation that just operates in memory maybe.

[bpasero]

There is now an InMemoryBackupFileService whenever there is no backupPath configured.