T73268: Link C/C++ unit tests into single executable

This commit introduces a new way to build unit tests. It is now possible
for each module to generate its own test library. The tests in these
libraries are then bundled into a single executable.

The test executable can be run with `ctest`. Even though the tests
reside in a single executable, they are still exposed as individual
tests to `ctest`, and thus can be selected via its `-R` argument.

Not yet ported tests still build & run as before.

The following rules apply:

- Test code should reside in the same directory as the code under test.
- Tests that target functionality in `somefile.{c,cc}` should reside in
  `somefile_test.cc`.
- The namespace for tests is the `tests` sub-namespace of the code under
  test. For example, tests for `blender::bke` should be in
  `blender::bke:tests`.
- The test files should be listed in the module's `CMakeLists.txt` in a
  `blender_add_test_lib()` call. See the `blenkernel` module for an
  example.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D7649

2 files changed, 88 insertions, 0 deletions

diff --git a/tests/gtests/runner/CMakeLists.txt b/tests/gtests/runner/CMakeLists.txt
new file mode 100644
index 00000000000..e7cbabfe7c6
--- /dev/null
+++ b/tests/gtests/runner/CMakeLists.txt
@@ -0,0 +1,63 @@
+# ***** BEGIN GPL LICENSE BLOCK *****
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software Foundation,
+# Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+#
+# The Original Code is Copyright (C) 2020, Blender Foundation
+# All rights reserved.
+# ***** END GPL LICENSE BLOCK *****
+
+# Build the test runner. This runner takes care of running all GTests, i.e.
+# the code that was built using the blender_add_test_lib() CMake macro (see
+# macros.cmake).
+set(SRC
+  blender_test.cc
+)
+
+if(WITH_BUILDINFO)
+  list(APPEND SRC
+    "$<TARGET_OBJECTS:buildinfoobj>"
+  )
+endif()
+
+
+# Test libraries need to be linked "whole archive", because they're not
+# directly referenced from other code.
+get_property(_test_libs GLOBAL PROPERTY BLENDER_TEST_LIBS)
+if(WIN32)
+  list(APPEND TEST_LIBS ${_test_libs})
+elseif(APPLE)
+  list(APPEND TEST_LIBS "-Wl,-force_load" ${_test_libs})
+elseif(UNIX)
+  list(APPEND TEST_LIBS "-Wl,--whole-archive" ${_test_libs} "-Wl,--no-whole-archive")
+else()
+  message(FATAL_ERROR "Unknown how to link whole-archive with your compiler ${CMAKE_CXX_COMPILER_ID}")
+endif()
+unset(_test_libs)
+
+# This builds `bin/tests/blender_test`, but does not add it as a single test.
+setup_libdirs()
+BLENDER_SRC_GTEST_EX(
+  NAME blender
+  SRC "${SRC}"
+  EXTRA_LIBS "${TEST_LIBS}"
+  SKIP_ADD_TEST
+)
+setup_liblinks(blender_test)
+
+# This runs the blender_test executable with `--gtest_list_tests`, then
+# exposes those tests individually to the ctest runner.
+# See https://cmake.org/cmake/help/v3.18/module/GoogleTest.html
+include(GoogleTest)
+gtest_discover_tests(blender_test)
diff --git a/tests/gtests/runner/blender_test.cc b/tests/gtests/runner/blender_test.cc
new file mode 100644
index 00000000000..fbce7a4283f
--- /dev/null
+++ b/tests/gtests/runner/blender_test.cc
@@ -0,0 +1,25 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2020 Blender Foundation.
+ * All rights reserved.
+ */
+
+/* This file is intentionally left blank. It is necessary for CMake to have a source file for each
+ * executable. However, the blender_tests test runner only comprises of statically linked library
+ * files, including its main function.
+ *
+ * See source/blender/blenkernel/CMakeLists.txt for an example of how to add unit tests to the test
+ * runner. */