Add unit test.

asserts/snapasserts/export_test.go

@@ -0,0 +1,21 @@
+// -*- Mode: Go; indent-tabs-mode: t -*-
+
+/*
+ * Copyright (C) 2021 Canonical Ltd
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+package snapasserts
+
+type ByRevision = byRevision

asserts/snapasserts/validation_sets_test.go

@@ -21,6 +21,7 @@ package snapasserts_test
 
 import (
 	"fmt"
+	"sort"
 
 	. "gopkg.in/check.v1"
 
@@ -644,3 +645,10 @@ func (s *validationSetsSuite) TestCheckInstalledSnapsErrorFormat(c *C) {
 		c.Assert(err, ErrorMatches, tc.errorMsg, Commentf("#%d: ", i))
 	}
 }
+
+func (s *validationSetsSuite) TestSortByRevision(c *C) {
+	revs := []snap.Revision{snap.R(10), snap.R(4), snap.R(5), snap.R(-1)}
+
+	sort.Sort(snapasserts.ByRevision(revs))
+	c.Assert(revs, DeepEquals, []snap.Revision{snap.R(-1), snap.R(4), snap.R(5), snap.R(10)})
+}