when maglevd rehashes its config:

- when a backend gets newly added or restarted, an event should fire; perhaps transition to 'unknown'
- when a backend gets removed, an event should fire; perhaps transition to 'removed'
- when a backend is in 'unknown' state, fast-interval is appropriate

internal/health/state_test.go

@@ -169,9 +169,13 @@ func TestNextInterval(t *testing.T) {
 
 	b := New("test", net.ParseIP("10.0.0.1"), 2, 3) // max=4
 
-	// Unknown (no probes yet): always use interval, never downInterval.
-	if got := b.NextInterval(interval, fast, down); got != interval {
-		t.Errorf("StateUnknown: got %v, want %v (interval)", got, interval)
+	// Unknown: use fast-interval to establish state quickly.
+	if got := b.NextInterval(interval, fast, down); got != fast {
+		t.Errorf("StateUnknown with fast: got %v, want %v (fast)", got, fast)
+	}
+	// Unknown, no fast-interval configured: fall back to interval.
+	if got := b.NextInterval(interval, 0, down); got != interval {
+		t.Errorf("StateUnknown without fast: got %v, want %v (interval)", got, interval)
 	}
 
 	// After first fail: counter=0, state=Down → downInterval.
@@ -291,6 +295,40 @@ func TestTransitionTimestamp(t *testing.T) {
 	}
 }
 
+func TestStartRemove(t *testing.T) {
+	b := newBackend()
+
+	// Start records an unknown→unknown transition.
+	tr := b.Start(5)
+	if tr.From != StateUnknown || tr.To != StateUnknown {
+		t.Errorf("Start transition: got %s→%s, want unknown→unknown", tr.From, tr.To)
+	}
+	if len(b.Transitions) != 1 {
+		t.Errorf("transitions after Start: got %d, want 1", len(b.Transitions))
+	}
+	if b.State != StateUnknown {
+		t.Errorf("state after Start: got %s, want unknown", b.State)
+	}
+
+	// Remove transitions to StateRemoved.
+	b.State = StateUp
+	tr = b.Remove(5)
+	if tr.From != StateUp || tr.To != StateRemoved {
+		t.Errorf("Remove transition: got %s→%s, want up→removed", tr.From, tr.To)
+	}
+	if b.State != StateRemoved {
+		t.Errorf("state after Remove: got %s, want removed", b.State)
+	}
+
+	// Record is a no-op once removed.
+	if b.Record(pass(), 5) {
+		t.Error("Record should not transition a removed backend")
+	}
+	if b.State != StateRemoved {
+		t.Errorf("state changed after Record on removed backend: %s", b.State)
+	}
+}
+
 func TestStateString(t *testing.T) {
 	cases := []struct {
 		s    State
@@ -300,6 +338,7 @@ func TestStateString(t *testing.T) {
 		{StateUp, "up"},
 		{StateDown, "down"},
 		{StatePaused, "paused"},
+		{StateRemoved, "removed"},
 	}
 	for _, c := range cases {
 		if c.s.String() != c.want {