When I use Spring and want to write a unit test, I can specify a custom context configuration in various ways, for example, by providing a different path of the context.xml.
But I don't see the way how to do that for CDI if I want to use a custom dependencies configuration for testing in the same maven module.
The documentation is very strict about this point:
For EJB modules or JAR files, the beans.xml deployment descriptor, if present, must be in the META-INF directory.
If there is already /META-INF/beans.xml in the sources, I can not place a different one into the test-resources (it simply will be ignored).
Is any way to configure Weld/CDI, may be by using some system variables, to change the path of the beans.xml?
For EJB modules or JAR files, the beans.xml deployment descriptor, if present, must be in the META-INF directory.
That is true, however that concerns an already created/packaged JAR which you then use as a dependency of your app. But your app can have it's own beans.xml too. beans.xml is just a means to define one bean archive and certain structures (interceptors, decorators, ...) within that archive. That means, for instance, that an interceptor enabled via beans.xml inside that JAR library will not be enabled in your application unless you specify it in beans.xml of that app too. Hence the link you see between the documentation and the testing you are asking about might not be correct/relevant. Not sure if I got you right there, though.
Is any way to configure Weld, may be through using some system variables, to change the path of the beans.xml?
No, there isn't. But in EE you mostly test with Arquillian and that allows you (among other things) to define a test deployment. There you can include any custom beans.xml you desire. That's also what Weld/CDI TCK tests use most of the time.