state: fix service unit removal

state/unit_test.go

 package state_test
 
 import (
         . "launchpad.net/gocheck"
         "launchpad.net/juju-core/charm"
         "launchpad.net/juju-core/state"
         "launchpad.net/juju-core/state/api/params"
         "sort"
         "strconv"
         "time"
@@ skipping 696 matching lines @@
         c.Assert(err, IsNil)
         err = s.unit.Refresh()
         c.Assert(state.IsNotFound(err), Equals, true)
         units, err := s.service.AllUnits()
         c.Assert(err, IsNil)
         c.Assert(units, HasLen, 0)
         err = s.unit.Remove()
         c.Assert(err, IsNil)
 }
 
+func (s *UnitSuite) TestRemovePathological(c *C) {
+        // Add a relation between wordpress and mysql...
+        wordpress := s.service
+        wordpress0 := s.unit
+        mysql, err := s.State.AddService("mysql", s.AddTestingCharm(c, "mysql"))
+        c.Assert(err, IsNil)
+        eps, err := s.State.InferEndpoints([]string{"wordpress", "mysql"})
+        c.Assert(err, IsNil)
+        rel, err := s.State.AddRelation(eps...)
+        c.Assert(err, IsNil)
+
+        // Enter scope with a unit of mysql, to keep the relation (and thus
+        // wordpress itself) from being removed.
+        mysql0, err := mysql.AddUnit()
+        c.Assert(err, IsNil)
+        mysql0ru, err := rel.Unit(mysql0)
+        c.Assert(err, IsNil)
+        err = mysql0ru.EnterScope(nil)
+        c.Assert(err, IsNil)

[thumper, 2013/04/15 23:03:24]

It isn't obvious to me what these commands are here for at all.  Perhaps in the
future we could have some higher level testing functions that make the tests
more readable and understandable dealing with higher level concepts.

[fwereade, 2013/04/16 00:56:04]

I *think* that everything I could say here on top of the existing comments is
covered in doc/.

+
+        // Destroy wordpress, and remove its last unit.
+        err = wordpress.Destroy()
+        c.Assert(err, IsNil)
+        err = wordpress0.EnsureDead()
+        c.Assert(err, IsNil)
+        err = wordpress0.Remove()
+        c.Assert(err, IsNil)
+
+        // Check this didn't kill the service or relation yet...
+        err = wordpress.Refresh()
+        c.Assert(err, IsNil)
+        err = rel.Refresh()
+        c.Assert(err, IsNil)
+
+        // ...but finally leaving relation scope on the other side does.
+        err = mysql0ru.LeaveScope()
+        c.Assert(err, IsNil)
+        err = wordpress.Refresh()
+        c.Assert(state.IsNotFound(err), Equals, true)
+        err = rel.Refresh()
+        c.Assert(state.IsNotFound(err), Equals, true)
+}
+
 func (s *UnitSuite) TestWatchSubordinates(c *C) {
         w := s.unit.WatchSubordinateUnits()
         defer stop(c, w)
         assertChange := func(units ...string) {
                 s.State.Sync()
                 select {
                 case ch, ok := <-w.Changes():
                         c.Assert(ok, Equals, true)
                         if len(units) > 0 {
                                 sort.Strings(ch)
@@ skipping 180 matching lines @@
         err := s.unit.SetAnnotations(annotations)
         c.Assert(err, IsNil)
         err = s.unit.EnsureDead()
         c.Assert(err, IsNil)
         err = s.unit.Remove()
         c.Assert(err, IsNil)
         ann, err := s.unit.Annotations()
         c.Assert(err, IsNil)
         c.Assert(ann, DeepEquals, make(map[string]string))
 }