Documentation: clarify that TEST_DEVS is optional

Signed-off-by: Omar Sandoval <osandov@fb.com>

diff --git a/Documentation/running-tests.md b/Documentation/running-tests.md
index ea2ce85bf243e3a066a14531aa4bc463fa115193..a479d5e94c5e06a56f7725036c79313abcb0d3e3 100644 (file)
--- a/Documentation/running-tests.md
+++ b/Documentation/running-tests.md
@@ -32,6 +32,9 @@ and will overwrite any data on these devices.
 TEST_DEVS=(/dev/nvme0n1 /dev/sdb)
 ```
 
+If `TEST_DEVS` is not defined or is empty, only tests which do not require a
+device will be run.
+
 ### Excluding Tests