RFC: Make ECMAddTests respect BUILD_TESTING

Summary:
Use-case: Make building unit tests optional, by just following the CMake
BUILD_TESTING option.

The usual approach to conditionally build tests is to do:
```
if (BUILD_TESTING)
    add_executable(TestOne TestOne.cpp)
    target_link_libraries(TestOne my_library)
endif()
```

or:

```
if (BUILD_TESTING)
    add_subdirectory(tests)
endif()
```

This patch just turns all calls to ecm_add_test(...) into no-ops if
BUILD_TESTING=OFF.

See:
  https://cmake.org/cmake/help/v3.6/module/CTest.html

Reviewers: vkrause

Reviewed By: vkrause

Subscribers: kossebau, vkrause, elvisangelaccio, asturmlechner, apol, #frameworks, #build_system

Tags: #frameworks, #build_system

Differential Revision: https://phabricator.kde.org/D7187

1 files changed, 10 insertions, 0 deletions

diff --git a/modules/ECMAddTests.cmake b/modules/ECMAddTests.cmake
index 96673888..c77a7aaf 100644
--- a/modules/ECMAddTests.cmake
+++ b/modules/ECMAddTests.cmake
@@ -49,6 +49,12 @@
 # be given; this will be used for both the target and test names (and, as with
 # ecm_add_tests(), the NAME_PREFIX argument will be prepended to the test name).
 #
+# If BUILD_TESTING is set to OFF, ecm_add_test will turn into a no-op and thus
+# will not add any test-related targets
+#
+# BUILD_TESTING is created as a cache variable by the CTest module and by the
+# :kde-module:`KDECMakeSettings` module.
+#
 #
 # Since pre-1.0.0.
 
@@ -84,6 +90,10 @@ include(ECMMarkAsTest)
 include(ECMMarkNonGuiExecutable)
 
 function(ecm_add_test)
+  if(NOT BUILD_TESTING)
+      return() # turn this function into a no-op
+  endif()
+
   set(options GUI)
   # TARGET_NAME_VAR and TEST_NAME_VAR are undocumented args used by
   # ecm_add_tests