diff --git a/test/README.markdown b/test/README.markdown
index b3128de..6922f4a 100644
--- a/test/README.markdown
+++ b/test/README.markdown
@@ -22,3 +22,10 @@ call Setup()
 - Inspect output from the new test.  If good, copy it to `foo.ok`.
 - Run the tests to ensure new test's output is verified.
 - `rm *.out` and commit changes.
+
+### Limitations
+
+- Currently tests are done by writing out a file and comparing it to a known good one.
+- Only 1 file per test is supported.
+- There's no support for assertions within the testcase code.
+