From 52b4a9125eb391e652afa838e601a51caf31b406 Mon Sep 17 00:00:00 2001
From: Sandro Elsweijer <sandro.elsweijer@dlr.de>
Date: Wed, 21 Aug 2024 09:14:47 +0200
Subject: [PATCH] let tests run in parallel as default

---
 CMakeLists.txt      |  2 +-
 test/CMakeLists.txt | 14 ++++++++++++--
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index ec64d7f618..f06b37a63a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -29,7 +29,7 @@ option( T8CODE_BUILD_DOCUMENTATION "Build t8code's documentation" OFF )
 include(CMakeDependentOption)
 cmake_dependent_option( T8CODE_BUILD_DOCUMENTATION_SPHINX "Build t8code's documentation using sphinx" OFF "T8CODE_BUILD_DOCUMENTATION" OFF )
 
-set(T8CODE_CUSTOM_TEST_COMMAND "" CACHE STRING "Define custom test command, e.g.: mpirun -n 4")
+set(T8CODE_CUSTOM_TEST_COMMAND "" CACHE STRING "Define custom test command, e.g.: mpirun -np 8 (overwrites standard mpirun -np 4 if build with mpi)")
 
 if( NOT CMAKE_BUILD_TYPE )
     set( CMAKE_BUILD_TYPE "Release" )
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 33ce3ffd72..3b86619d98 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -11,9 +11,19 @@ function( add_t8_test )
     target_link_libraries( ${ADD_T8_TEST_NAME} PRIVATE T8 gtest pthread)
 
     # Split custom test command into a list by whitespace.
-    separate_arguments (T8CODE_CUSTOM_TEST_COMMAND_LIST NATIVE_COMMAND "${T8CODE_CUSTOM_TEST_COMMAND}")
+    # If MPI is enabled, and no custom test command is provided, use mpirun -np 4 as the default command.
+    # If MPI is not enabled, use the custom test command as is.
+    if ( T8CODE_ENABLE_MPI )
+        if ( T8CODE_CUSTOM_TEST_COMMAND STREQUAL "" )
+            separate_arguments (T8CODE_TEST_COMMAND_LIST NATIVE_COMMAND "mpirun -np 4")
+        else ( T8CODE_CUSTOM_TEST_COMMAND STREQUAL "" )
+            separate_arguments (T8CODE_TEST_COMMAND_LIST NATIVE_COMMAND ${T8CODE_CUSTOM_TEST_COMMAND})
+        endif ( T8CODE_CUSTOM_TEST_COMMAND STREQUAL "" )
+    else( T8CODE_ENABLE_MPI )
+        separate_arguments (T8CODE_TEST_COMMAND_LIST NATIVE_COMMAND ${T8CODE_CUSTOM_TEST_COMMAND})
+    endif ( T8CODE_ENABLE_MPI )
 
-    add_test( NAME ${ADD_T8_TEST_NAME} COMMAND ${T8CODE_CUSTOM_TEST_COMMAND_LIST} ./${ADD_T8_TEST_NAME} )
+    add_test( NAME ${ADD_T8_TEST_NAME} COMMAND ${T8CODE_TEST_COMMAND_LIST} ./${ADD_T8_TEST_NAME} )
 endfunction()
 
 # Copy test files to build folder so that the t8_test programs can find them.