It only happens in hybird mode.

Both jdk.jndi and jdk.jndi.internal have been included in tested module-info.java.
It still throws below exception:
================
STATUS:Failed.Failed: javax.naming.NoInitialContextException: Cannot instantiate class: com.sun.jndi.ldap.LdapCtxFactory [Root exception is java.lang.ClassNotFoundException: com.sun.jndi.ldap.LdapCtxFactory : requested by +test.hybrid ]
STATUS:Failed.Failed: javax.naming.NoInitialContextException: Cannot instantiate class: com.sun.jndi.ldap.LdapCtxFactory [Root exception is java.lang.ClassNotFoundException: com.sun.jndi.ldap.LdapCtxFactory : requested by +test.hybrid]
================

It looks LdapCtxFactory has been included in lib/modules/jdk.jndi/8-ea/classes really:
================
gtee@jsn-sb2500-5: ~ $ jar -tf /java/sqe/comp/jsn/users/amylu/jigsaw/solaris-amd64/lib/modules/jdk.jndi/8-ea/classes | grep LdapCtxFactory
com/sun/jndi/ldap/LdapCtxFactory.class
================

It fails only because it is not exported in jmod. Below is a output fragment of "jmod ls -v". It does not include com.sun.jndi.ldap package in jdk.jndi category
======================
jdk.jndi@8-ea
  requires local jdk.auth.internal@=8-ea
  requires local jdk.base.internal@=8-ea
  requires optional jdk.desktop@=8-ea
  requires jdk.rmi@=8-ea
  requires jdk.tls.internal@=8-ea
  requires synthesized java.base@>=7
  requires service optional javax.naming.ldap.StartTlsResponse
  provides javax.naming
  provides service sun.net.spi.nameservice.NameServiceDescriptor with sun.net.spi.nameservice.dns.DNSNameServiceDescriptor
  exports
    com.sun.security.auth
    com.sun.security.auth.module
    javax.naming
    javax.naming.directory
    javax.naming.event
    javax.naming.ldap
    javax.naming.spi
  view jdk.jndi.internal
    permits jdk.cosnaming, jdk.kerberos
    exports
      com.sun.jndi.toolkit.url
      com.sun.security.auth
      com.sun.security.auth.module
      javax.naming
      javax.naming.directory
      javax.naming.event
      javax.naming.ldap
      javax.naming.spi
      sun.net.dns
======================