allwatcher_internal_test.go:1078:
    func() {
        checkIsolationForEnv := func(st *State, w, otherW *testWatcher) {
            c.Logf("Making changes to model %s", st.ModelUUID())

            if test.setUpState != nil {
                test.setUpState(st)
                // Consume events from setup.
                w.AssertChanges(c)
                w.AssertNoChange(c)
                otherW.AssertNoChange(c)
            }

            test.triggerEvent(st)
            // Check event was isolated to the correct watcher.
            w.AssertChanges(c)
            w.AssertNoChange(c)
            otherW.AssertNoChange(c)
        }
        otherState := s.newState(c)

        w1 := newTestAllWatcher(s.state, c)
        defer w1.Stop()
        w2 := newTestAllWatcher(otherState, c)
        defer w2.Stop()

        // The first set of deltas is empty, reflecting an empty model.
        w1.AssertNoChange(c)
        w2.AssertNoChange(c)
        checkIsolationForEnv(s.state, w1, w2)
        checkIsolationForEnv(otherState, w2, w1)
    }()
allwatcher_internal_test.go:3106:
    c.Assert(len(d), gc.Equals, 0)
... obtained int = 1
... expected int = 0