Update demo notes BOOST UTF in preCICE

Author: uekerman

05_testing_and_ci/boost_testing_precice_demo.md

@@ -10,15 +10,15 @@ Look around preCICE in the terminal + text editor.
     - Imports `testing/Testing.hpp`, there we handle UTF imports
     - Test suite for `math` namespace and test suite per file (here `math/differences.hpp`)
     - `BOOST_CHECK` actually not recommended to use. Is used internally by `BOOST_TEST`.
-    - Powerful macro `PRECICE_TEST(1_rank)`; here it means that this test is run on one MPI rank
-        - Tests are normally run on 4 MPI ranks to test parallel implementation and to mimic different coupled solvers
+    - Powerful macro `PRECICE_TEST()` to setup test context (resources, singletons, not data)
 
 ## Unit vs. Integration Tests
 
 - Clear separation in preCICE: integration tests only directly use API of preCICE.
 - They are located in `tests` folder.
-- Look at `tests/serial/initialize-data/Explicit.cpp`
-    - Explain `PRECICE_TEST` and how it is used
+- Look at `tests/serial/initialize-data/Explicit.cpp`:
+    - Explain `PRECICE_TEST_SETUP` and how it is used: test is run on two MPI ranks living in seperate MPI communicators.
+    - Information can be accessed via `context`.
     - More information: [blog post on bssw.io on multiphysics testing](https://bssw.io/blog_posts/overcoming-complexity-in-testing-multiphysics-coupling-software)
 
 ## White-Box Testing
@@ -34,18 +34,18 @@ Look around preCICE in the terminal + text editor.
     - Has public and private members. We want to check the private members in tests.
     - Does not `friend` every test, but only `WaveformFixture`
     - `src/testing/WaveformFixture.hpp` has functions to access private members
-    - This fixture is used in many tests in `src/time/tests/WaveformTests`
+    - This fixture is used in many tests in `src/time/tests/WaveformTests` (but not handed over to test like normal UTF fixtures)
 
 ## Test Matrices
 
 - Look at `tests/serial/mapping-nearest-projection/QuadMappingDiagonalNearestProjectionEdgesTallKite.cpp`:
     - Define test matrix with data sets: `boost::unit_test::data::make`
 
-## Test Context
+## Boost Test Context
 
 - Look at `src/mapping/tests/NearestProjectionMappingTest.cpp`:
     - `BOOST_TEST_CONTEXT` outputs context information on failure
 
 ## CMake
 
-- Look at `cmake/CTestConfig.cmake`: More things tested than only UTF
+- Look at `cmake/CTestConfig.cmake`: Complicated, but more things tested than only UTF (search for `add_test`)