[cairo] [PATCH] Document how to run passable tests in test/README

[Darxus]

---
 test/README | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/test/README b/test/README
index 9ed9bc7..6ff3ec1 100644
--- a/test/README
+++ b/test/README
@@ -35,6 +35,29 @@ CAIRO_TEST_TARGET environment variable, so for instance:
 This binary should be backwards-compatible with all library versions,
 allowing you to compare current versus past behaviour for any test.
 
+Avoiding tests known to fail
+----------------------------
+
+As of August 2016, there are a number of tests known to fail even with
+updated references, by generating diffenet output each run, or crashing.
+The following will get the maximum number of targets to pass, by using
+freshly generated reference images (which should not be necessary).  This
+may be useful for generating new references, making changes to cairo, then
+running the tests against your references, before submitting your changes.
+
+  Xvfb -screen 0 1680x1024x24 -ac -nolisten tcp :2 &
+
+  ./autogen.sh --enable-xcb
+  make
+  # To update reference images, will error:
+  DISPLAY=:2 CAIRO_TEST_TARGET=xcb,image,image16 make test
+  # The new reference images:
+  cp -a test/output/ $HOME/cairo-ref.xcb-image.xvfb
+
+  ./autogen.sh --enable-xcb
+  make
+  DISPLAY=:2 CAIRO_REF_DIR=$HOME/cairo-ref.xcb-image.xvfb CAIRO_TEST_TARGET=xcb,image,image16 make test
+
 Tailoring tests running
 -----------------------
 There are some mechanisms to limit the tests run during "make test".
-- 
2.7.4