Make a reftest for the flights app.

sky/HACKING.md

 Hacking on Sky
 ==============
 
 Building
 --------
 
 * Follow the setup & build instructions for [Mojo](https://github.com/domokit/mojo)
 
 Running applications
 --------------------
@@ skipping 23 matching lines @@
 * Write tests in [mocha format](http://visionmedia.github.io/mocha/#getting-started) and use [chai asserts](http://chaijs.com/api/assert/):
 ```html
 describe('My pretty test of my subject', function() {
   var subject = new MySubject();
 
   it('should be pretty', function() {
     assert.ok(subject.isPretty);
   });
 });
 ```
+
+Adding pixel tests
+------------------
+
+Sky does not have proper pixel tests. Instead we have only reftests.
+If you want a pixel test, you need to dump the png from a reftest,
+upload it to googlestorage and then put and <img> pointing to the
+uploaded file in the reference.
+
+1. Create your test (e.g. foo.sky).
+2. Create an dummy reference file (foo-expected.sky).
+3. Run the test (it will fail).
+4. Copy the -actual.png file to googlestorage (see below).
+5. Put an <img> pointing to your newly uploaded png in the reference file.
+
+Copying the file to googlestorage:
+$ sha1sum ../out/Debug/layout-test-results/framework/flights-app-pixels-actual.png
+db0508cdfe69e996a93464050dc383f6480f1283  ../out/Debug/layout-test-results/framework/flights-app-pixels-actual.png
+$ gsutil.py cp ../out/Debug/layout-test-results/framework/flights-app-pixels-actual.png gs://mojo/sky-pngs/db0508cdfe69e996a93464050dc383f6480f1283
+
+Long-term, we should not have these tests at all and should just
+dump paint commands. In the short-term, if we find we're doing this
+a lot we should obviously automate this process, e.g. test_sky could
+do all of this work, including spitting out the correct reference file.