diff --git a/runtime/doc/testing.txt b/runtime/doc/testing.txt
index 1147673..15c5498 100644
--- a/runtime/doc/testing.txt
+++ b/runtime/doc/testing.txt
@@ -20,11 +20,17 @@
 Vim can be tested after building it, usually with "make test".
 The tests are located in the directory "src/testdir".
 
+There are two types of tests added over time:
+	test20.in		oldest, only for tiny and small builds
+	test_something.vim	new style tests
+
 						*new-style-testing*
 New tests should be added as new style tests.  The test scripts are named
 test_<feature>.vim (replace <feature> with the feature under test). These use
 functions such as |assert_equal()| to keep the test commands and the expected
 result in one place.
+						*old-style-testing*
+These tests are used only for testing Vim without the |+eval| feature.
 
 Find more information in the file src/testdir/README.txt.