CITest: check if test dependencies exist

Make it a CMake error in case a test dependency does not exist.

AtlasTest/CITest/README.md

@@ -63,6 +63,7 @@ atlas_add_citest( Test2 ...
 )
 ```
 Use `DEPENDS_SUCCESS` if the test should only run if the dependee(s) succeeded.
+If used, `DEPENDS[_SUCCESS]` needs to be specified as the **last argument** of `atlas_add_citest`.
 
 Additional requirements can be specified via e.g.
 ```cmake

AtlasTest/CITest/cmake/CITestFunctions.cmake

@@ -46,6 +46,9 @@ function( atlas_add_citest testName )
    # test dependencies that are only run on success of the dependee(s):
    if( ARG_DEPENDS_SUCCESS )
       foreach( _test ${ARG_DEPENDS_SUCCESS} )
+         if( NOT TEST "CITest_${_test}_ctest" )
+            message( SEND_ERROR "${testName} declares dependency on ${_test} which does not exist" )
+         endif()
          set_property( TEST CITest_${testName}_ctest
             APPEND PROPERTY FIXTURES_REQUIRED "CITest_${_test}_fixture" )
       endforeach()