doc: explain why block, char devices aren't tested

1 files changed, 9 insertions, 0 deletions

diff --git a/summain.md b/summain.md
index df2087e..47acba4 100644
--- a/summain.md
+++ b/summain.md
@@ -65,6 +65,15 @@ order.
 
 # Acceptance criteria
 
+These scenarios verify that Summain handles the various kinds of file
+system objects it may encounter, with two exceptions: block and
+character devices. To create those, one needs to be the `root` user,
+and we don't want to have to run the test suite as root. Instead, we
+blithely rely on the output being correct for those anyway. Testing
+manually indicates that it works, and the only difference from, say,
+regular files is that the mode starts with a `b` or `c`, which is
+exactly correct.
+
 ## Directory
 
 ~~~scenario