[!755] Fix/issue 183 skipped tests

Merge branch 'fix/issue-183-skipped-tests' into 'master'

ref:core/dune-common Fixes [#183].

See merge request [!755]

  [#183]: gitlab.dune-project.org/NoneNone/issues/183
  [!755]: gitlab.dune-project.org/core/dune-common/merge_requests/755


Closes #183

cmake/modules/DuneTestMacros.cmake

@@ -374,14 +374,13 @@ function(dune_add_test)
       set(ACTUAL_NAME ${ADDTEST_NAME})
       set(ACTUAL_CMD_ARGS ${ADDTEST_CMD_ARGS})
       if(TARGET "${ADDTEST_COMMAND}")
+        # if the target name is specified as command, expand to full path using the TARGET_FILE generator expression
         set(ACTUAL_TESTCOMMAND "$<TARGET_FILE:${ADDTEST_COMMAND}>")
       else()
-        # this should only happen if this is an EXPECT_COMPILE_FAIL test,
-        # as we set ADDTEST_COMMAND to cmake in this case.
-        # Or if we run the test via some script.
         set(ACTUAL_TESTCOMMAND "${ADDTEST_COMMAND}")
       endif()
 
+      # modify test name and command for parallel tests
       if(NOT ${procnum} STREQUAL "1")
         set(ACTUAL_NAME "${ACTUAL_NAME}-mpi-${procnum}")
         set(ACTUAL_CMD_ARGS ${MPIEXEC_PREFLAGS} ${MPIEXEC_NUMPROC_FLAG} ${procnum} "${ACTUAL_TESTCOMMAND}" ${MPIEXEC_POSTFLAGS} ${ACTUAL_CMD_ARGS})
@@ -390,7 +389,7 @@ function(dune_add_test)
 
       # if this is a skipped test because a guard was false, overwrite the command
       if(SHOULD_SKIP_TEST)
-        set(ACTUAL_TESTCOMMAND "$<TARGET_FILE:${ADDTEST_COMMAND}>")
+        set(ACTUAL_TESTCOMMAND "$<TARGET_FILE:${ADDTEST_TARGET}>")
         set(ACTUAL_CMD_ARGS)
       endif()