func (s *provisionerSuite) TestWatchFilesystemAttachments(c *gc.C) {
	s.setupFilesystems(c)
	c.Assert(s.resources.Count(), gc.Equals, 0)

	args := params.Entities{Entities: []params.Entity{
		{"machine-0"},
		{s.State.ModelTag().String()},
		{"environ-adb650da-b77b-4ee8-9cbb-d57a9a592847"},
		{"machine-1"},
		{"machine-42"}},
	}
	result, err := s.api.WatchFilesystemAttachments(args)
	c.Assert(err, jc.ErrorIsNil)
	sort.Sort(byMachineAndEntity(result.Results[0].Changes))
	sort.Sort(byMachineAndEntity(result.Results[1].Changes))
	c.Assert(result, jc.DeepEquals, params.MachineStorageIdsWatchResults{
		Results: []params.MachineStorageIdsWatchResult{
			{
				MachineStorageIdsWatcherId: "1",
				Changes: []params.MachineStorageId{{
					MachineTag:    "machine-0",
					AttachmentTag: "filesystem-0-0",
				}},
			},
			{
				MachineStorageIdsWatcherId: "2",
				Changes: []params.MachineStorageId{{
					MachineTag:    "machine-0",
					AttachmentTag: "filesystem-1",
				}, {
					MachineTag:    "machine-0",
					AttachmentTag: "filesystem-2",
				}, {
					MachineTag:    "machine-2",
					AttachmentTag: "filesystem-3",
				}},
			},
			{Error: apiservertesting.ErrUnauthorized},
			{Error: apiservertesting.ErrUnauthorized},
			{Error: apiservertesting.ErrUnauthorized},
		},
	})

	// Verify the resources were registered and stop them when done.
	c.Assert(s.resources.Count(), gc.Equals, 2)
	v0Watcher := s.resources.Get("1")
	defer statetesting.AssertStop(c, v0Watcher)
	v1Watcher := s.resources.Get("2")
	defer statetesting.AssertStop(c, v1Watcher)

	// Check that the Watch has consumed the initial events ("returned" in
	// the Watch call)
	wc := statetesting.NewStringsWatcherC(c, s.State, v0Watcher.(state.StringsWatcher))
	wc.AssertNoChange()
	wc = statetesting.NewStringsWatcherC(c, s.State, v1Watcher.(state.StringsWatcher))
	wc.AssertNoChange()
}

func (s *InstancePollerSuite) TestWatchModelMachinesSuccess(c *gc.C) {
	// Add a couple of machines.
	s.st.SetMachineInfo(c, machineInfo{id: "2"})
	s.st.SetMachineInfo(c, machineInfo{id: "1"})

	expectedResult := params.StringsWatchResult{
		Error:            nil,
		StringsWatcherId: "1",
		Changes:          []string{"1", "2"}, // initial event (sorted ids)
	}
	result, err := s.api.WatchModelMachines()
	c.Assert(err, jc.ErrorIsNil)
	c.Assert(result, jc.DeepEquals, expectedResult)

	// Verify the watcher resource was registered.
	c.Assert(s.resources.Count(), gc.Equals, 1)
	resource1 := s.resources.Get("1")
	defer func() {
		if resource1 != nil {
			statetesting.AssertStop(c, resource1)
		}
	}()

	// Check that the watcher has consumed the initial event
	wc1 := statetesting.NewStringsWatcherC(c, s.st, resource1.(state.StringsWatcher))
	wc1.AssertNoChange()

	s.st.CheckCallNames(c, "WatchModelMachines")

	// Add another watcher to verify events coalescence.
	result, err = s.api.WatchModelMachines()
	c.Assert(err, jc.ErrorIsNil)
	expectedResult.StringsWatcherId = "2"
	c.Assert(result, jc.DeepEquals, expectedResult)
	s.st.CheckCallNames(c, "WatchModelMachines", "WatchModelMachines")
	c.Assert(s.resources.Count(), gc.Equals, 2)
	resource2 := s.resources.Get("2")
	defer statetesting.AssertStop(c, resource2)
	wc2 := statetesting.NewStringsWatcherC(c, s.st, resource2.(state.StringsWatcher))
	wc2.AssertNoChange()

	// Remove machine 1, check it's reported.
	s.st.RemoveMachine(c, "1")
	wc1.AssertChangeInSingleEvent("1")

	// Make separate changes, check they're combined.
	s.st.SetMachineInfo(c, machineInfo{id: "2", life: state.Dying})
	s.st.SetMachineInfo(c, machineInfo{id: "3"})
	s.st.RemoveMachine(c, "42") // ignored
	wc1.AssertChangeInSingleEvent("2", "3")
	wc2.AssertChangeInSingleEvent("1", "2", "3")

	// Stop the first watcher and assert its changes chan is closed.
	c.Assert(resource1.Stop(), jc.ErrorIsNil)
	wc1.AssertClosed()
	resource1 = nil
}

func (s *ActionSuite) TestUnitWatchActionNotifications(c *gc.C) {
	// get units
	unit1, err := s.State.Unit(s.unit.Name())
	c.Assert(err, jc.ErrorIsNil)
	preventUnitDestroyRemove(c, unit1)

	unit2, err := s.State.Unit(s.unit2.Name())
	c.Assert(err, jc.ErrorIsNil)
	preventUnitDestroyRemove(c, unit2)

	// queue some actions before starting the watcher
	fa1, err := unit1.AddAction("snapshot", nil)
	c.Assert(err, jc.ErrorIsNil)
	fa2, err := unit1.AddAction("snapshot", nil)
	c.Assert(err, jc.ErrorIsNil)

	// set up watcher on first unit
	w := unit1.WatchActionNotifications()
	defer statetesting.AssertStop(c, w)
	wc := statetesting.NewStringsWatcherC(c, s.State, w)
	// make sure the previously pending actions are sent on the watcher
	expect := expectActionIds(fa1, fa2)
	wc.AssertChange(expect...)
	wc.AssertNoChange()

	// add watcher on unit2
	w2 := unit2.WatchActionNotifications()
	defer statetesting.AssertStop(c, w2)
	wc2 := statetesting.NewStringsWatcherC(c, s.State, w2)
	wc2.AssertChange()
	wc2.AssertNoChange()

	// add action on unit2 and makes sure unit1 watcher doesn't trigger
	// and unit2 watcher does
	fa3, err := unit2.AddAction("snapshot", nil)
	c.Assert(err, jc.ErrorIsNil)
	wc.AssertNoChange()
	expect2 := expectActionIds(fa3)
	wc2.AssertChange(expect2...)
	wc2.AssertNoChange()

	// add a couple actions on unit1 and make sure watcher sees events
	fa4, err := unit1.AddAction("snapshot", nil)
	c.Assert(err, jc.ErrorIsNil)
	fa5, err := unit1.AddAction("snapshot", nil)
	c.Assert(err, jc.ErrorIsNil)

	expect = expectActionIds(fa4, fa5)
	wc.AssertChange(expect...)
	wc.AssertNoChange()
}

func (s *AddresserSuite) TestWatchIPAddresses(c *gc.C) {
	c.Assert(s.resources.Count(), gc.Equals, 0)

	s.st.addIPAddressWatcher("0.1.2.3", "0.1.2.4", "0.1.2.7")

	result, err := s.api.WatchIPAddresses()
	c.Assert(err, jc.ErrorIsNil)
	c.Assert(result, gc.DeepEquals, params.EntitiesWatchResult{
		EntitiesWatcherId: "1",
		Changes: []string{
			"ipaddress-00000000-1111-2222-3333-0123456789ab",
			"ipaddress-00000000-1111-2222-4444-0123456789ab",
			"ipaddress-00000000-1111-2222-7777-0123456789ab",
		},
		Error: nil,
	})

	// Verify the resource was registered and stop when done.
	c.Assert(s.resources.Count(), gc.Equals, 1)
	resource := s.resources.Get("1")
	defer statetesting.AssertStop(c, resource)

	// Check that the Watch has consumed the initial event ("returned" in
	// the Watch call)
	wc := statetesting.NewStringsWatcherC(c, s.st, resource.(state.StringsWatcher))
	wc.AssertNoChange()
}

func (s *deployerSuite) TestWatchUnits(c *gc.C) {
	c.Assert(s.resources.Count(), gc.Equals, 0)

	args := params.Entities{Entities: []params.Entity{
		{Tag: "machine-1"},
		{Tag: "machine-0"},
		{Tag: "machine-42"},
	}}
	result, err := s.deployer.WatchUnits(args)
	c.Assert(err, jc.ErrorIsNil)
	sort.Strings(result.Results[0].Changes)
	c.Assert(result, gc.DeepEquals, params.StringsWatchResults{
		Results: []params.StringsWatchResult{
			{Changes: []string{"logging/0", "mysql/0"}, StringsWatcherId: "1"},
			{Error: apiservertesting.ErrUnauthorized},
			{Error: apiservertesting.ErrUnauthorized},
		},
	})

	// Verify the resource was registered and stop when done
	c.Assert(s.resources.Count(), gc.Equals, 1)
	c.Assert(result.Results[0].StringsWatcherId, gc.Equals, "1")
	resource := s.resources.Get("1")
	defer statetesting.AssertStop(c, resource)

	// Check that the Watch has consumed the initial event ("returned" in
	// the Watch call)
	wc := statetesting.NewStringsWatcherC(c, s.State, resource.(state.StringsWatcher))
	wc.AssertNoChange()
}

func (s *serviceSuite) TestWatchRelations(c *gc.C) {
	w, err := s.apiService.WatchRelations()
	c.Assert(err, jc.ErrorIsNil)
	defer statetesting.AssertStop(c, w)
	wc := statetesting.NewStringsWatcherC(c, s.BackingState, w)

	// Initial event.
	wc.AssertChange()
	wc.AssertNoChange()

	// Change something other than the lifecycle and make sure it's
	// not detected.
	err = s.wordpressService.SetExposed()
	c.Assert(err, jc.ErrorIsNil)
	wc.AssertNoChange()

	// Add another service and relate it to wordpress,
	// check it's detected.
	s.addMachineServiceCharmAndUnit(c, "mysql")
	rel := s.addRelation(c, "wordpress", "mysql")
	wc.AssertChange(rel.String())

	// Destroy the relation and check it's detected.
	err = rel.Destroy()
	c.Assert(err, jc.ErrorIsNil)
	wc.AssertChange(rel.String())
	wc.AssertNoChange()

	statetesting.AssertStop(c, w)
	wc.AssertClosed()
}

func (s *watcherSuite) TestStringsWatcherStopsWithPendingSend(c *gc.C) {
	// Call the Deployer facade's WatchUnits for machine-0.
	var results params.StringsWatchResults
	args := params.Entities{Entities: []params.Entity{{Tag: s.rawMachine.Tag().String()}}}
	err := s.stateAPI.Call("Deployer", "", "WatchUnits", args, &results)
	c.Assert(err, gc.IsNil)
	c.Assert(results.Results, gc.HasLen, 1)
	result := results.Results[0]
	c.Assert(result.Error, gc.IsNil)

	// Start a StringsWatcher and check the initial event.
	w := watcher.NewStringsWatcher(s.stateAPI, result)
	wc := statetesting.NewStringsWatcherC(c, s.State, w)

	// Create a service, deploy a unit of it on the machine.
	mysql := s.AddTestingService(c, "mysql", s.AddTestingCharm(c, "mysql"))
	principal, err := mysql.AddUnit()
	c.Assert(err, gc.IsNil)
	err = principal.AssignToMachine(s.rawMachine)
	c.Assert(err, gc.IsNil)

	// Ensure the initial event is delivered. Then test the watcher
	// can be stopped cleanly without reading the pending change.
	s.BackingState.StartSync()
	statetesting.AssertCanStopWhenSending(c, w)
	wc.AssertClosed()
}

func (s *withoutStateServerSuite) TestWatchEnvironMachines(c *gc.C) {
	c.Assert(s.resources.Count(), gc.Equals, 0)

	got, err := s.provisioner.WatchEnvironMachines()
	c.Assert(err, gc.IsNil)
	want := params.StringsWatchResult{
		StringsWatcherId: "1",
		Changes:          []string{"0", "1", "2", "3", "4"},
	}
	c.Assert(got.StringsWatcherId, gc.Equals, want.StringsWatcherId)
	c.Assert(got.Changes, jc.SameContents, want.Changes)

	// Verify the resources were registered and stop them when done.
	c.Assert(s.resources.Count(), gc.Equals, 1)
	resource := s.resources.Get("1")
	defer statetesting.AssertStop(c, resource)

	// Check that the Watch has consumed the initial event ("returned"
	// in the Watch call)
	wc := statetesting.NewStringsWatcherC(c, s.State, resource.(state.StringsWatcher))
	wc.AssertNoChange()

	// Make sure WatchEnvironMachines fails with a machine agent login.
	anAuthorizer := s.authorizer
	anAuthorizer.MachineAgent = true
	anAuthorizer.EnvironManager = false
	aProvisioner, err := provisioner.NewProvisionerAPI(s.State, s.resources, anAuthorizer)
	c.Assert(err, gc.IsNil)

	result, err := aProvisioner.WatchEnvironMachines()
	c.Assert(err, gc.ErrorMatches, "permission denied")
	c.Assert(result, gc.DeepEquals, params.StringsWatchResult{})
}

func (s *firewallerBaseSuite) testWatchModelMachines(
	c *gc.C,
	facade interface {
		WatchModelMachines() (params.StringsWatchResult, error)
	},
) {
	c.Assert(s.resources.Count(), gc.Equals, 0)

	got, err := facade.WatchModelMachines()
	c.Assert(err, jc.ErrorIsNil)
	want := params.StringsWatchResult{
		StringsWatcherId: "1",
		Changes:          []string{"0", "1", "2"},
	}
	c.Assert(got.StringsWatcherId, gc.Equals, want.StringsWatcherId)
	c.Assert(got.Changes, jc.SameContents, want.Changes)

	// Verify the resources were registered and stop them when done.
	c.Assert(s.resources.Count(), gc.Equals, 1)
	resource := s.resources.Get("1")
	defer statetesting.AssertStop(c, resource)

	// Check that the Watch has consumed the initial event ("returned"
	// in the Watch call)
	wc := statetesting.NewStringsWatcherC(c, s.State, resource.(state.StringsWatcher))
	wc.AssertNoChange()
}

func (s *VolumeStateSuite) TestWatchMachineVolumeAttachments(c *gc.C) {
	service := s.setupMixedScopeStorageService(c, "block")
	addUnit := func() {
		u, err := service.AddUnit()
		c.Assert(err, jc.ErrorIsNil)
		err = s.State.AssignUnit(u, state.AssignCleanEmpty)
		c.Assert(err, jc.ErrorIsNil)
	}
	addUnit()

	w := s.State.WatchMachineVolumeAttachments(names.NewMachineTag("0"))
	defer testing.AssertStop(c, w)
	wc := testing.NewStringsWatcherC(c, s.State, w)
	wc.AssertChangeInSingleEvent("0:0", "0:0/1", "0:0/2") // initial
	wc.AssertNoChange()

	addUnit()
	// no change, since we're only interested in the one machine.
	wc.AssertNoChange()

	err := s.State.DetachVolume(names.NewMachineTag("0"), names.NewVolumeTag("0"))
	c.Assert(err, jc.ErrorIsNil)
	wc.AssertChangeInSingleEvent("0:0") // dying
	wc.AssertNoChange()

	err = s.State.RemoveVolumeAttachment(names.NewMachineTag("0"), names.NewVolumeTag("0"))
	c.Assert(err, jc.ErrorIsNil)
	wc.AssertChangeInSingleEvent("0:0") // removed
	wc.AssertNoChange()

	// TODO(axw) respond to changes to the same machine when we support
	// dynamic storage and/or placement.
}

func (s *VolumeStateSuite) TestWatchEnvironVolumeAttachments(c *gc.C) {
	service := s.setupMixedScopeStorageService(c, "block")
	addUnit := func() {
		u, err := service.AddUnit()
		c.Assert(err, jc.ErrorIsNil)
		err = s.State.AssignUnit(u, state.AssignCleanEmpty)
		c.Assert(err, jc.ErrorIsNil)
	}
	addUnit()

	w := s.State.WatchEnvironVolumeAttachments()
	defer testing.AssertStop(c, w)
	wc := testing.NewStringsWatcherC(c, s.State, w)
	wc.AssertChangeInSingleEvent("0:0") // initial
	wc.AssertNoChange()

	addUnit()
	wc.AssertChangeInSingleEvent("1:3")
	wc.AssertNoChange()

	err := s.State.DetachVolume(names.NewMachineTag("0"), names.NewVolumeTag("0"))
	c.Assert(err, jc.ErrorIsNil)
	wc.AssertChangeInSingleEvent("0:0") // dying
	wc.AssertNoChange()

	err = s.State.RemoveVolumeAttachment(names.NewMachineTag("0"), names.NewVolumeTag("0"))
	c.Assert(err, jc.ErrorIsNil)
	wc.AssertChangeInSingleEvent("0:0") // removed
	wc.AssertNoChange()
}

func (s *unitSuite) TestWatchActionNotifications(c *gc.C) {
	w, err := s.apiUnit.WatchActionNotifications()
	c.Assert(err, jc.ErrorIsNil)

	defer statetesting.AssertStop(c, w)
	wc := statetesting.NewStringsWatcherC(c, s.BackingState, w)

	// Initial event.
	wc.AssertChange()

	// Add a couple of actions and make sure the changes are detected.
	action, err := s.wordpressUnit.AddAction("fakeaction", map[string]interface{}{
		"outfile": "foo.txt",
	})
	c.Assert(err, jc.ErrorIsNil)
	wc.AssertChange(action.Id())

	action, err = s.wordpressUnit.AddAction("fakeaction", map[string]interface{}{
		"outfile": "foo.bz2",
		"compression": map[string]interface{}{
			"kind":    "bzip",
			"quality": float64(5.0),
		},
	})
	c.Assert(err, jc.ErrorIsNil)
	wc.AssertChange(action.Id())

	statetesting.AssertStop(c, w)
	wc.AssertClosed()
}

func (s *provisionerSuite) TestWatchEnvironMachines(c *gc.C) {
	w, err := s.provisioner.WatchEnvironMachines()
	c.Assert(err, gc.IsNil)
	defer statetesting.AssertStop(c, w)
	wc := statetesting.NewStringsWatcherC(c, s.BackingState, w)

	// Initial event.
	wc.AssertChange(s.machine.Id())

	// Add another 2 machines make sure they are detected.
	otherMachine, err := s.State.AddMachine("quantal", state.JobHostUnits)
	c.Assert(err, gc.IsNil)
	otherMachine, err = s.State.AddMachine("quantal", state.JobHostUnits)
	c.Assert(err, gc.IsNil)
	wc.AssertChange("1", "2")

	// Change the lifecycle of last machine.
	err = otherMachine.EnsureDead()
	c.Assert(err, gc.IsNil)
	wc.AssertChange("2")

	// Add a container and make sure it's not detected.
	template := state.MachineTemplate{
		Series: "quantal",
		Jobs:   []state.MachineJob{state.JobHostUnits},
	}
	_, err = s.State.AddMachineInsideMachine(template, s.machine.Id(), instance.LXC)
	c.Assert(err, gc.IsNil)
	wc.AssertNoChange()

	statetesting.AssertStop(c, w)
	wc.AssertClosed()
}

func (s *PortsDocSuite) TestWatchPorts(c *gc.C) {
	w := s.State.WatchOpenedPorts()
	c.Assert(w, gc.NotNil)

	defer statetesting.AssertStop(c, w)
	wc := statetesting.NewStringsWatcherC(c, s.State, w)
	wc.AssertChange()
	wc.AssertNoChange()

	portRange := state.PortRange{
		FromPort: 100,
		ToPort:   200,
		UnitName: s.unit1.Name(),
		Protocol: "TCP",
	}
	globalKey := state.PortsGlobalKey(s.machine.Id(), network.DefaultPublic)
	err := s.ports.OpenPorts(portRange)
	c.Assert(err, gc.IsNil)
	wc.AssertChange(globalKey)

	err = s.ports.Refresh()
	c.Assert(err, gc.IsNil)
	err = s.ports.ClosePorts(portRange)
	c.Assert(err, gc.IsNil)
	wc.AssertChange(globalKey)
}

func (s *FilesystemStateSuite) TestWatchMachineFilesystemAttachments(c *gc.C) {
	service := s.setupMixedScopeStorageService(c, "filesystem")
	addUnit := func() {
		u, err := service.AddUnit()
		c.Assert(err, jc.ErrorIsNil)
		err = s.State.AssignUnit(u, state.AssignCleanEmpty)
		c.Assert(err, jc.ErrorIsNil)
	}
	addUnit()

	w := s.State.WatchMachineFilesystemAttachments(names.NewMachineTag("0"))
	defer testing.AssertStop(c, w)
	wc := testing.NewStringsWatcherC(c, s.State, w)
	wc.AssertChangeInSingleEvent("0:0", "0:0/1", "0:0/2") // initial
	wc.AssertNoChange()

	addUnit()
	// no change, since we're only interested in the one machine.
	wc.AssertNoChange()

	// TODO(axw) respond to changes to the same machine when we support
	// dynamic storage and/or placement.
	// TODO(axw) respond to Dying/Dead when we have
	// the means to progress Filesystem lifecycle.
}

func (s *deployerSuite) TestWatchUnits(c *gc.C) {
	// TODO(dfc) fix state.Machine to return a MachineTag
	machine, err := s.st.Machine(s.machine.Tag().(names.MachineTag))
	c.Assert(err, gc.IsNil)
	w, err := machine.WatchUnits()
	c.Assert(err, gc.IsNil)
	defer statetesting.AssertStop(c, w)
	wc := statetesting.NewStringsWatcherC(c, s.BackingState, w)

	// Initial event.
	wc.AssertChange("mysql/0", "logging/0")
	wc.AssertNoChange()

	// Change something other than the lifecycle and make sure it's
	// not detected.
	err = s.subordinate.SetPassword("foo")
	c.Assert(err, gc.ErrorMatches, "password is only 3 bytes long, and is not a valid Agent password")
	wc.AssertNoChange()

	err = s.subordinate.SetPassword("foo-12345678901234567890")
	c.Assert(err, gc.IsNil)
	wc.AssertNoChange()

	// Make the subordinate dead and check it's detected.
	err = s.subordinate.EnsureDead()
	c.Assert(err, gc.IsNil)
	wc.AssertChange("logging/0")
	wc.AssertNoChange()

	statetesting.AssertStop(c, w)
	wc.AssertClosed()
}

func (s *machineSuite) TestWatchUnits(c *gc.C) {
	w, err := s.apiMachine.WatchUnits()
	c.Assert(err, gc.IsNil)
	defer statetesting.AssertStop(c, w)
	wc := statetesting.NewStringsWatcherC(c, s.BackingState, w)

	// Initial event.
	wc.AssertChange("wordpress/0")
	wc.AssertNoChange()

	// Change something other than the life cycle and make sure it's
	// not detected.
	err = s.machines[0].SetPassword("foo")
	c.Assert(err, gc.ErrorMatches, "password is only 3 bytes long, and is not a valid Agent password")
	wc.AssertNoChange()

	err = s.machines[0].SetPassword("foo-12345678901234567890")
	c.Assert(err, gc.IsNil)
	wc.AssertNoChange()

	// Unassign unit 0 from the machine and check it's detected.
	err = s.units[0].UnassignFromMachine()
	c.Assert(err, gc.IsNil)
	wc.AssertChange("wordpress/0")
	wc.AssertNoChange()

	statetesting.AssertStop(c, w)
	wc.AssertClosed()
}

func (s *ActionSuite) TestWatchActionNotifications(c *gc.C) {
	svc := s.AddTestingService(c, "dummy2", s.charm)
	u, err := svc.AddUnit()
	c.Assert(err, jc.ErrorIsNil)

	w := u.WatchActionNotifications()
	defer statetesting.AssertStop(c, w)
	wc := statetesting.NewStringsWatcherC(c, s.State, w)
	wc.AssertChange()
	wc.AssertNoChange()

	// add 3 actions
	fa1, err := u.AddAction("snapshot", nil)
	c.Assert(err, jc.ErrorIsNil)
	fa2, err := u.AddAction("snapshot", nil)
	c.Assert(err, jc.ErrorIsNil)
	fa3, err := u.AddAction("snapshot", nil)
	c.Assert(err, jc.ErrorIsNil)

	// fail the middle one
	action, err := s.State.Action(fa2.Id())
	c.Assert(err, jc.ErrorIsNil)
	_, err = action.Finish(state.ActionResults{Status: state.ActionFailed, Message: "die scum"})
	c.Assert(err, jc.ErrorIsNil)

	// expect the first and last one in the watcher
	expect := expectActionIds(fa1, fa3)
	wc.AssertChange(expect...)
	wc.AssertNoChange()
}

func (s *watcherSuite) TestWatchUnitsKeepsEvents(c *gc.C) {
	// Create two services, relate them, and add one unit to each - a
	// principal and a subordinate.
	mysql := s.AddTestingService(c, "mysql", s.AddTestingCharm(c, "mysql"))
	logging := s.AddTestingService(c, "logging", s.AddTestingCharm(c, "logging"))
	eps, err := s.State.InferEndpoints([]string{"mysql", "logging"})
	c.Assert(err, gc.IsNil)
	rel, err := s.State.AddRelation(eps...)
	c.Assert(err, gc.IsNil)
	principal, err := mysql.AddUnit()
	c.Assert(err, gc.IsNil)
	err = principal.AssignToMachine(s.rawMachine)
	c.Assert(err, gc.IsNil)
	relUnit, err := rel.Unit(principal)
	c.Assert(err, gc.IsNil)
	err = relUnit.EnterScope(nil)
	c.Assert(err, gc.IsNil)
	subordinate, err := logging.Unit("logging/0")
	c.Assert(err, gc.IsNil)

	// Call the Deployer facade's WatchUnits for machine-0.
	var results params.StringsWatchResults
	args := params.Entities{Entities: []params.Entity{{Tag: s.rawMachine.Tag().String()}}}
	err = s.stateAPI.Call("Deployer", "", "WatchUnits", args, &results)
	c.Assert(err, gc.IsNil)
	c.Assert(results.Results, gc.HasLen, 1)
	result := results.Results[0]
	c.Assert(result.Error, gc.IsNil)

	// Start a StringsWatcher and check the initial event.
	w := watcher.NewStringsWatcher(s.stateAPI, result)
	wc := statetesting.NewStringsWatcherC(c, s.State, w)
	wc.AssertChange("mysql/0", "logging/0")
	wc.AssertNoChange()

	// Now, without reading any changes advance the lifecycle of both
	// units, inducing an update server-side after each two changes to
	// ensure they're reported as separate events over the API.
	err = subordinate.EnsureDead()
	c.Assert(err, gc.IsNil)
	s.BackingState.StartSync()
	err = subordinate.Remove()
	c.Assert(err, gc.IsNil)
	err = principal.EnsureDead()
	c.Assert(err, gc.IsNil)
	s.BackingState.StartSync()

	// Expect these changes as 2 separate events, so that
	// nothing gets lost.
	wc.AssertChange("logging/0")
	wc.AssertChange("mysql/0")
	wc.AssertNoChange()

	statetesting.AssertStop(c, w)
	wc.AssertClosed()
}

func (s *ActionSuite) TestUnitWatchActionResults(c *gc.C) {
	unit1, err := s.State.Unit(s.unit.Name())
	c.Assert(err, gc.IsNil)
	preventUnitDestroyRemove(c, unit1)

	unit2, err := s.State.Unit(s.unit2.Name())
	c.Assert(err, gc.IsNil)
	preventUnitDestroyRemove(c, unit2)

	action0, err := unit1.AddAction("fakeaction", nil)
	c.Assert(err, gc.IsNil)
	action1, err := unit2.AddAction("fakeaction", nil)
	c.Assert(err, gc.IsNil)
	action2, err := unit1.AddAction("fakeaction", nil)
	c.Assert(err, gc.IsNil)

	err = action2.Finish(state.ActionResults{Status: state.ActionFailed})
	c.Assert(err, gc.IsNil)
	err = action1.Finish(state.ActionResults{Status: state.ActionCompleted})
	c.Assert(err, gc.IsNil)

	w1 := unit1.WatchActionResults()
	defer statetesting.AssertStop(c, w1)
	wc1 := statetesting.NewStringsWatcherC(c, s.State, w1)
	expect := expectActionResultIds(unit1, "1")
	wc1.AssertChange(expect...)
	wc1.AssertNoChange()

	w2 := unit2.WatchActionResults()
	defer statetesting.AssertStop(c, w2)
	wc2 := statetesting.NewStringsWatcherC(c, s.State, w2)
	expect = expectActionResultIds(unit2, "0")
	wc2.AssertChange(expect...)
	wc2.AssertNoChange()

	err = action0.Finish(state.ActionResults{Status: state.ActionCompleted})
	c.Assert(err, gc.IsNil)

	expect = expectActionResultIds(unit1, "0")
	wc1.AssertChange(expect...)
	wc1.AssertNoChange()
}