Currently zxid does not ship with an IdP (though the necessary protocol encoders and decoders are latently available in libzxid, should anyone wish to make an attempt to hack an IdP together). For you to test zxid, you will need to acquire an IdP from somewhere - any vendor whose product is SAML 2.0 certified will do. Possible sources are
http://symlabs.com/Products/SFIAM.html who have a free download of commercial product
Lasso: http://lasso.entrouvert.org/
If you do not want to install an IdP yourself (even for testing), find someone who already runs one and ask if they would be willing to load the metadata of your zxid SP. If you do this, you will need to get externally visible domain names. This canned tutorial uses /etc/hosts (see previous step) which is only visible on your own machine.
Once you get your IdP up and running, you need to make sure it accepts
the zxid SP in its Circle of Trust (CoT). This is done by placing
the metadata of the SP in right place in the IdP product configuration.
If your IdP supports automatic CoT management, just turn it on
and chances are you are done.
If not, you can obtain the zxid SP metadata (which is slightly different for each install so you can't just copy it from existing install) from
https://sp1.zxidsp.org:8443/zxid?o=B
This URL is the well known location method metadata URL. It is also the SP Entity ID or Provider ID, should the IdP product ask for this in its configuration. If the IdP product needs you to supply the metadata manually as an xml file, just point your web browser to the above URL and save to file, or use curl(1) or wget(1).
zxid SP, by default, has automatic fetching of IdP metadata enabled so there is no manual configuration step needed, provided that the IdP supports the well known location method. All SAML 2.0 certified IdP implementations must support it (but you may still need to enable it in configuration). See [SAML2meta] section 4.1 "Publication and Resolution via Well-Known Location", p.29, for normative description of this method.
However, you will need the Entity ID (Provider ID) of the IdP. This is the URL that the IdP uses for well known location method of metadata sharing. You may need to dig the IdP documentation or GUI for a while to find it. If you already have the IdP metadata as an xml file, open it and look for EntityDescriptor/entityID. If you already have the file, you can also import it manually by running the following command
./zxid -import file:///path/to/idp-meta.xml
But the preferred method still is: just let the automatic method do its job.