To test your eduID.at-registered SAML Service Provider (SP) with a SAML Identity Provider you can make use of the ACOnet OpenIDP, where you can register an account online and subsequently use the OpenIDP for logins to your SAML SP. You may also make use of the ACOnet-provided Discovery Services, though integrating IDP Discovery with the service is strongly recommended for User Experience reasons, cf. REFEDS Discovery Guide.
For testing with actual production IDPs of eduID.at member institutions you can directly contact the IDP admins of those institutions (preferably ones you already have dealings with, unsolicited requests will potentially not be appreciated), e.g. by using the Technical Contacts from the SAML metadata, also rendered in this listing of ACOnet-registered IDPs.
Of course you can always contact ACOnet for help with finding a member IDP to test against.