diff --git a/sim/README.rst b/sim/README.rst
index 305a57d..5bf2aac 100644
--- a/sim/README.rst
+++ b/sim/README.rst
@@ -38,6 +38,13 @@
 the relevant modules from mcuboot, build the simulator, and run the
 tests.
 
+There are several different features you can test. For example,
+testing RSA signatures can be done with::
+
+  $ cargo test --features sig-rsa
+
+For a complete list of features, see Cargo.toml.
+
 Debugging
 =========