Tests: move tests from USD test directory into `io/common` and `io/usd`

This commit is a followup of {D7649}, and ports the USD tests to the new
testing approach. It moves test code from `tests/gtests/usd` into
`source/blender/io/common` and `source/blender/io/usd`, and adjusts the
use of namespaces to be consistent with the other tests.

I decided to put one test into `io/usd/tests`, instead of
`io/usd/intern`. The reason is that this test does not correspond with a
single file in that directory; instead, it tests Blender's integration
with the USD library itself.

There are two new CLI arguments for the Big Test Runner:

- `--test-assets-dir`, which points to the `lib/tests` directory in the
  SVN repository. This allows unit tests to find test assets.
- `--test-release-dir`, which points to `bin/{BLENDER_VERSION}` in the
  build directory. At the moment this is only used by the USD test.

The CLI arguments are automatically passed to the Big Test Runner when
using `ctest`. When manually running the tests, the arguments are only
required when there is a test run that needs them.

For more info about splitting some code into 'common', see
rB084c5d6c7e2cf8.

No functional changes to the tests themselves, only to the way they are
built & run.

Differential Revision: https://developer.blender.org/D8314

Reviewed by: brecht, mont29

2 files changed, 34 insertions, 0 deletions

diff --git a/tests/gtests/testing/testing.h b/tests/gtests/testing/testing.h
index 32cb6e7f18a..34928035b7d 100644
--- a/tests/gtests/testing/testing.h
+++ b/tests/gtests/testing/testing.h
@@ -7,6 +7,15 @@
 #include "glog/logging.h"
 #include "gtest/gtest.h"
 
+namespace blender::tests {
+
+/* These strings are passed on the CLI with the --test-asset-dir and --test-release-dir arguments.
+ * The arguments are added automatically when invoking tests via `ctest`. */
+const std::string &flags_test_asset_dir();   /* ../lib/tests in the SVN directory. */
+const std::string &flags_test_release_dir(); /* bin/{blender version} in the build directory. */
+
+}  // namespace blender::tests
+
 #define EXPECT_V3_NEAR(a, b, eps) \
   { \
     EXPECT_NEAR(a[0], b[0], eps); \
diff --git a/tests/gtests/testing/testing_main.cc b/tests/gtests/testing/testing_main.cc
index 6b3a8e5515d..0acdcf3a8a5 100644
--- a/tests/gtests/testing/testing_main.cc
+++ b/tests/gtests/testing/testing_main.cc
@@ -19,6 +19,31 @@
 
 #include "testing/testing.h"
 
+DEFINE_string(test_assets_dir, "", "lib/tests directory from SVN containing the test assets.");
+DEFINE_string(test_release_dir, "", "bin/{blender version} directory of the current build.");
+
+namespace blender::tests {
+
+const std::string &flags_test_asset_dir()
+{
+  if (FLAGS_test_assets_dir.empty()) {
+    ADD_FAILURE()
+        << "Pass the flag --test-assets-dir and point to the lib/tests directory from SVN.";
+  }
+  return FLAGS_test_assets_dir;
+}
+
+const std::string &flags_test_release_dir()
+{
+  if (FLAGS_test_release_dir.empty()) {
+    ADD_FAILURE()
+        << "Pass the flag --test-release-dir and point to the bin/{blender version} directory.";
+  }
+  return FLAGS_test_release_dir;
+}
+
+}  // namespace blender::tests
+
 int main(int argc, char **argv)
 {
   testing::InitGoogleTest(&argc, argv);