upgrader: new WatchForEnvironConfigChanges

state/state_test.go

 // Copyright 2012, 2013 Canonical Ltd.
 // Licensed under the AGPLv3, see LICENCE file for details.
 
 package state_test
 
 import (
         "fmt"
         "labix.org/v2/mgo/bson"
         . "launchpad.net/gocheck"
         "launchpad.net/juju-core/charm"
@@ skipping 1075 matching lines @@
                 case <-time.After(500 * time.Millisecond):
                         c.Fatalf("did not get change: %#v", change)
                 }
                 assertNoChange()
         }
         assertChange(nil)
         assertChange(attrs{"default-series": "another-series"})
         assertChange(attrs{"fancy-new-key": "arbitrary-value"})
 }
 
+// setAgentVersion sets the current agent version in the state's
+// environment configuration.
+func setAgentVersion(st *state.State, vers version.Number) error {
+        cfg, err := st.EnvironConfig()
+        if err != nil {
+                return err
+        }
+        cfg, err = cfg.Apply(map[string]interface{}{"agent-version": vers.String()})
+        if err != nil {
+                panic(fmt.Errorf("config refused agent-version: %v", err))
+        }
+        return st.SetEnvironConfig(cfg)
+}
+
+func (s *StateSuite) TestWatchForEnvironConfigChanges(c *C) {
+        cur := version.Current.Number
+        err := setAgentVersion(s.State, cur)
+        c.Assert(err, IsNil)
+        w := s.State.WatchForEnvironConfigChanges()
+        defer statetesting.AssertStop(c, w)
+
+        wc := statetesting.NewNotifyWatcherC(c, s.State, w)
+        // Initially we get one change notification
+        wc.AssertOneChange()
+
+        // Multiple changes will only result in a single change notification
+        newVersion := cur
+        newVersion.Minor += 1
+        err = setAgentVersion(s.State, newVersion)
+        c.Assert(err, IsNil)
+
+        newerVersion := newVersion
+        newerVersion.Minor += 1
+        err = setAgentVersion(s.State, newerVersion)
+        c.Assert(err, IsNil)
+        wc.AssertOneChange()
+
+        // Setting it to the same value does not trigger a change notification
+        err = setAgentVersion(s.State, newerVersion)
+        c.Assert(err, IsNil)
+        wc.AssertNoChange()
+}
+
 func (s *StateSuite) TestWatchEnvironConfigCorruptConfig(c *C) {
         cfg, err := s.State.EnvironConfig()
         c.Assert(err, IsNil)
 
         // Corrupt the environment configuration.
         settings := s.Session.DB("juju").C("settings")
         err = settings.UpdateId("e", bson.D{{"$unset", bson.D{{"name", 1}}}})
         c.Assert(err, IsNil)
 
         s.State.Sync()
@@ skipping 628 matching lines @@
         c.Assert(state.TopParentId("0"), Equals, "0")
         c.Assert(state.TopParentId("0/lxc/1"), Equals, "0")
         c.Assert(state.TopParentId("0/lxc/1/kvm/2"), Equals, "0")
 }
 
 func (s *StateSuite) TestParentId(c *C) {
         c.Assert(state.ParentId("0"), Equals, "")
         c.Assert(state.ParentId("0/lxc/1"), Equals, "0")
         c.Assert(state.ParentId("0/lxc/1/kvm/0"), Equals, "0/lxc/1")
 }