From 6390e36a4ef05633c19f22262269f2834985d3b7 Mon Sep 17 00:00:00 2001
From: David Wilson <dw@botanicus.net>
Date: Mon, 16 Apr 2018 14:27:55 +0100
Subject: [PATCH] tests: document selecting a target distribution.

---
 tests/README.md | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tests/README.md b/tests/README.md
index 4756541d..5cf7c1c5 100644
--- a/tests/README.md
+++ b/tests/README.md
@@ -30,6 +30,13 @@ and run the tests there.
 1. Run ``test``
 
 
+# Selecting a target distribution
+
+Docker target images exist for testing against CentOS and Debian, with the
+default being Debian. To select CentOS, specify `MITOGEN_TEST_DISTRO=centos` in
+the environment.
+
+
 # User Accounts
 
 A set of standard user account names are used by in the Docker container and