use gtest_discover_tests to regiester the unit tests

this modern approach registers many individual tests instead of a single monolitic test
so if one fails the rest continue running which allows the developer to flag multiple
failing tests on a single run
It also speeds up testing since tests run in parallel

Author: ericriff

tests/CMakeLists.txt

@@ -43,16 +43,19 @@ if(ament_cmake_FOUND)
 
 else()
 
+    enable_testing()
+
     find_package(GTest REQUIRED)
+    include(GoogleTest)
 
-    enable_testing()
     add_executable(behaviortree_cpp_test ${BT_TESTS})
-    add_test(NAME btcpp_test COMMAND behaviortree_cpp_test)
 
     target_link_libraries(behaviortree_cpp_test
         GTest::gtest
         GTest::gtest_main)
 
+    gtest_discover_tests(behaviortree_cpp_test)
+
 endif()
 
 target_include_directories(behaviortree_cpp_test PRIVATE include)