can't run multiple tests with adb

I can run my tests singularly using the following command:

C:\Google Drive\Testing>adb -s C4F12CC05723D6E shell am instrument -w -e class c
om.example.project.test.testcases.basictests.Test1 com.example.
http://ift.tt/1Y77bDM

com.example.project.test.testcases.basictests.test1:.

Time: 23.807

OK (1 test)

But I can't get all tests in the suite to run:

C:\Google Drive\Testing>adb -s C4F12CC05723D6E shell am instrument -w com.example
http://.project.test/android.support.test.runner.AndroidJUnitRunner


Time: 0

OK (0 tests)

I get the same result for trying to run a package of tests.

The runner doesn't seem to complain or anything, it just thinks there are 0 tests, when there are several.

I have the same problem when running the tests in android studio, I can run a single test but not the full suite or a full package.

I'm using espresso 2 which uses the AndroidJUnitRunner.

The test package is in the same project as the application being tested. The core application activities including the main activity reside in com.example.project and the test package is a subpackage of this; com.example.project.test

How do I investigate this problem?