To verifiy signatures in DigiDoc3 client, that have been created with test certificates it is needed to manually configure test certificates or the signature validation check will return status "Unknown". The configuration is different for old DDOC format and new BDOC/ASiC-E format.
Starting from DigiDoc3 client version 3.10 the certificate trustworthiness for documents in BDOC/ASiC-E format is determined with TSL lists ( Trust Service Status List ). TSL's are used for both document signing and signature validation.
It is possible to use digidoc-tool.exe command line program to validate BDOC and ASiC-E signatures, the program is located at DigiDoc3 client's installation directory. Instructions for using the command line program for creating and validating test signatures can be found here.
Alternatively, it is possible to validate BDOC/ASiC-E signatures with DigiDoc3 client application, if the default TSL list URL and TSL signature certificate data in the underlying Libdigidocpp library's source code are changed and the application is recompiled. Further instructions are provided here.
In DigiDoc3 client it's possible to validate DDOC files created with test certificates after installing the test certificate package from https://installer.id.ee/media/windows/Eesti_ID_kaart_testsertifikaadid.msi. Signatures given with test certificates can only be verified after installing test certificates.