Smoke tests are not independent

[planetmarshall]

Summary

The smoke tests provided in test_smoke.py are not independent, and their success depends on the order in which they are run

Expected Behaviour

The success of a test should be independent of the order in which it is run, and whether it is run in isolation or as part of a suite.

Actual Behaviour

Tests currently succeed only by coincidental choice of running order and specific expectation values

Steps to reproduce:

1. Modify test_single_config so that it asserts that a Debug config is installed (or anything except Release).
2. Run pytest -k test_single_config. The three selected tests should pass:

   collected 61 items / 58 deselected / 3 selected                                                                                                                      
   
   test_smoke.py::TestBasic::test_single_config PASSED                                                                [ 33%]
   test_smoke.py::TestBasic::test_single_config_only_one_configuration_installed PASSED        [ 66%]
   test_smoke.py::TestBasic::test_single_config_override_install_config PASSED                         [100%]
   

3. Move test_single_config so that it runs after test_single_config_override_install_config
   Run the tests again with pytest -k test_single_config. Now test_single_config will fail.

   collected 61 items / 58 deselected / 3 selected                                                                                                                      
   
   
   test_smoke.py::TestBasic::test_single_config_only_one_configuration_installed PASSED         [ 33%]
   test_smoke.py::TestBasic::test_single_config_override_install_config PASSED                          [66%]
   test_smoke.py::TestBasic::test_single_config FAILED                                                                   [100%]
   

4. If test_single_config is now run in isolation with pytest -k 'test_single_config and not test_single_config_o', it will pass