Ruei Chang's blog.

I got some failed item like the following below

com.android.cts.appsecurity.AdoptableHostTest#testAppsFAIL 

com.android.cts.appsecurity.AdoptableHostTest#testEjected FAIL 

com.android.cts.appsecurity.AdoptableHostTest#testPackageInstaller FAIL

com.android.cts.appsecurity.AdoptableHostTest#testPrimaryStorage FAIL 

All of these failed items give me the same log: Devices that claim to support adoptable storage must have adoptable media inserted during CTS to verify correct behavior

Here is a solution: 

First, do the factory reset then insert one USB disk and format it by Android.

Second, execute "adb shell sm set-force-adoptable true" to forced the disk in adoptable. Then run this test again, you might get pass of .com.android.cts.appsecurity.AdoptableHostTest