To determine what system modules are available in the runtime image jtreg executes GetJDKProperties with `--add-modules ALL-SYSTEM`. Incubator modules are not resolved when running with the ALL-SYSTEM token. This causes jtreg to not select tests that require, through the @modules tag, an incubator module.

The jdk.incubator.httpclient module is the only incubator module currently in JDK 9, so it can be used as an example here. Taking one test jdk/test/java/net/httpclient/BasicAuthTest.java

$ head -32 jdk/test/java/net/httpclient/BasicAuthTest.java | tail
/**
 * @test
 * @bug 8087112
 * @modules jdk.incubator.httpclient
 * jdk.httpserver
 * @run main/othervm BasicAuthTest
 * @summary Basic Authentication Test
 */

$ ~/tools/jtreg/bin/jtreg -v1 -ea -esa -noreport -jdk:../../build/linux-x86_64-normal-server-release/images/jdk java/net/httpclient/BasicAuthTest.java
Test results: no tests selected
Results written to /home/chhegar/repos/jdk9/dev/ssMove/jdk/test/JTwork

Note: the test is selected if run on an exploded build. This issue is specific to images since the incubator module's module-info.class has the ModuleResolution attributed added.

A temporary workaround is to run jtreg with `-javaoptions:--add-modules=jdk.incubator.httpclient`, but this is not really an option in JPRT, or other such infrastructure.