Jan, it doesn't matter if the jboss-ejb-client.properties in the classpath gets picked up and the (default) EJB client context uses that EJB receiver. What needs to be tested is to make sure that the JNDI context created in your test does not use that receiver and instead uses the receiver created for the scoped EJB client context.  For example: You can do this testing by creating the scoped client context to contain a EJB receiver with a specific user credential.

So, this test shouldn't be changing that system property. 

P.S: We already have a testcase which covers EJBCLIENT-34 org.jboss.as.test.multinode.remotecall.scoped.context.DynamicJNDIContextEJBInvocationTestCase but I don't mind including this new testcase after the recommended changes are done.