I took a look at Arquillian's implementation and saw that, for example the "ApplicationArchiveGenerator" interface has an SPI implementation file, with a given provider("DeploymentAnnotationArchiveGenerator"), and in the same time an "onlyOne" check when using it. I was wondering if this interface can be customized and extended, because that would be the scope of SPIs, taken in consideration that any customized class will not pass the "onlyOne" check.
That is correct.
ApplicationArchiveGenerator is a SPI point, but the SPI impl is 'hardcoded' at the moment.
Are you on irc? Can you step by #jbosstesting on irc.freenode.net and we can have a little chat about how we should do this.