Allow 16-bit avifImage in avifImageRGBToYUV()

Add tests.
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 11d1173..247ed7a 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -113,6 +113,16 @@
     target_include_directories(avifopaquetest PRIVATE ${GTEST_INCLUDE_DIRS})
     add_test(NAME avifopaquetest COMMAND avifopaquetest)
 
+    add_executable(avifpng16bittest gtest/avifpng16bittest.cc)
+    target_link_libraries(avifpng16bittest aviftest_helpers ${GTEST_LIBRARIES})
+    target_include_directories(avifpng16bittest PRIVATE ${GTEST_INCLUDE_DIRS})
+    add_test(NAME avifpng16bittest COMMAND avifpng16bittest ${CMAKE_CURRENT_SOURCE_DIR}/data/)
+
+    add_executable(avifreadimagetest gtest/avifreadimagetest.cc)
+    target_link_libraries(avifreadimagetest aviftest_helpers ${GTEST_LIBRARIES})
+    target_include_directories(avifreadimagetest PRIVATE ${GTEST_INCLUDE_DIRS})
+    add_test(NAME avifreadimagetest COMMAND avifreadimagetest ${CMAKE_CURRENT_SOURCE_DIR}/data/)
+
     add_executable(avifrgbtoyuvtest gtest/avifrgbtoyuvtest.cc)
     target_link_libraries(avifrgbtoyuvtest aviftest_helpers ${GTEST_BOTH_LIBRARIES})
     target_include_directories(avifrgbtoyuvtest PRIVATE ${GTEST_INCLUDE_DIRS})