validate_test: add TestCheckMandatoryFields
validate_test: add TestCheckMandatoryFields

Because there are so many cases, I only chose part of the test.

Signed-off-by: Zhou Hao <f577ade201aa03d612c19915a089dc6084d45cd9@cn.fujitsu.com>

liangchenye/ocitools,opencontainers/runtime-tools,liangchenye/ocitools,wking/ocitools-v2,opencontainers/runtime-tools,opencontainers/ocitools,wking/ocitools-v2,opencontainers/ocitools