Fix some ctest issues

[ottmar-zittlau]

This change addresses item #4408

This changes the behaviour of the test explorer tree view

The following changes are proposed:

• If tests are added in cmake via add_test and at the same time via gtest_discover_tests it can happen that the tree view doesn't work properly, because test descriptions from gtest_discover_tests are overwritten by those generated by add_test. I think the correct approach would be to only use one of these commands in cmake - but still I thought it would be a good idea to make it work. The fix works by reusing existing test items.

• Another thing that annoyed me was that the tree structure was changing when a test is run - I tried to capture the behaviour here:
  test_visibility_changes.webm

• I found out that cmake build is executed when tests are run - and afterwards the tests are refreshed. This refreshing works by removing all test items and re-building the tree structure. This caused all the items in the tree to be initialized in a certain state. I fixed this by keeping track of all the currently active test ids and removing the deleted ones at the end of the refresh-function.

Other Notes/Information

For the second issue I tried to figure out a way to avoid refreshing the tree if nothing has changed.
However, it seems as if this is not trivial. It could be possible to compute and store a hash (or something in this direction) of the json that is produced by cmake and use it as an indicator - let me know if you think it would be worthwhile to explore this direction.

Thanks and best regards
oz

[ottmar-zittlau]

@microsoft-github-policy-service agree