Skip building tests by default

[kkloberdanz]

CXX-1792
CXX-2702

Tests will not be compiled by default.
To enable building tests, build with -DBUILD_TESTING=ON

[vector-of-bool]

CMake has an semi-built-in option for this feature, BUILD_TESTING. At the top CMakeLists.txt, add:

if(NOT DEFINED BUILD_TESTING)
  set(BUILD_TESTING OFF)  # Set this to OFF by default
endif()
include(CTest)

[vector-of-bool]

I'm curious if this will work, but I haven't tested it:

if(NOT BUILD_TESTING)
  set_property(DIRECTORY PROPERTY EXCLUDE_FROM_ALL TRUE)
endif()

(and then the remainder of the file is reverted to as-it-was). IIUC, this should exclude every added target from the implicit all, but still defined them and are available for building by being named explicitly?

[kevinAlbs]

I agree with the suggestion to exclude test targets from all, but still have them defined.

Example: Targets in the examples directory are currently excluded from the all target with:

add_custom_target(examples DEPENDS ${MONGOCXX_EXAMPLE_EXECUTABLES} ${BSONCXX_EXAMPLE_EXECUTABLES})

But the example targets are still defined. CMake targets can be listed with cmake --build cmake-build --target help. An example target can be built by including the --target argument: cmake --build cmake-build --target aggregation_examples

[kkloberdanz]

This doesn't seem to work when I try it. The test programs are built by default when I implement this like so:

CMakeLists.txt:

if(NOT DEFINED BUILD_TESTING)
  set(BUILD_TESTING OFF)  # Set this to OFF by default
endif()

src/bsoncxx/test/CMakeLists.txt and src/mongocxx/test/CMakeLists.txt:

if(NOT BUILD_TESTING)
  set_property(DIRECTORY PROPERTY EXCLUDE_FROM_ALL TRUE)
endif()

include_directories(
  ...

[vector-of-bool]

Not sure if I can figure why the directory property doesn't work, so just discard that suggestion for now. On the other hand, the BUILD_TESTING variable should work? Are you sure to clear it from your cache before configuring?

[kkloberdanz]

I think I found the issue, and after applying the fix below, your suggestion then works. I pushed these changes and the tests are green.

-        set(ENABLE_TESTS OLD_ENABLE_TESTS)
-        set(BUILD_TESTING OLD_BUILD_TESTING)
+        set(ENABLE_TESTS ${OLD_ENABLE_TESTS})
+        set(BUILD_TESTING ${OLD_BUILD_TESTING})

[vector-of-bool]

LGTM. One more comment.

[vector-of-bool]

Suggest: Move this below project(). Will also want to include(CTest).

[kkloberdanz]

Based off our conversation in slack, we'll leave off the include(CTest) for now since it is currently causing the tests to be built unconditionally.