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Render Tests

Render, compositing and video sequencer tests compare render results against reference images.


Tests result can be inspected visually through a HTML file that shows both the new image, reference image and a diff. This can be found at:


Adding or Updating Tests

When adding a new test, or when there are benign test failures due to intentional changes, the reference images can be created or updated as follows:

cd ~/blender-git/build
# Update reference images for cycles tests
BLENDER_TEST_UPDATE=1 ctest -R cycles

After this all the tests should pass, and .blend files and references images can be committed. How to do so is explained here.



For testing Cycles GPU rendering, CYCLES_TEST_DEVICES in the CMake configuration is a list of devices to test. By default it is only CPU, but CUDA, OPTIX, ONEAPI, HIP and METAL can be added.

EEVEE and Workbench

WITH_GPU_RENDER_TESTS enables EEVEE and Workbench tests, which are currently disabled by default due to different outputs of different GPUs. They render the same .blend files as Cycles.


By default only CPU compositing is tested, but the GPU backend can also be tested by enabling WITH_COMPOSITOR_REALTIME_TESTS.


By default multiple tests are run with a single Blender launch, which speeds up test execution.

For investigating threading or memory corruption issues, disabling this can help avoid interference between tests. This is done by turning off WITH_TESTS_BATCHED.