Wait for the done key's grant, which the take-in writes after the compositions (issue 1945)

cmd/mesh-controller/composed_served_integration_test.go

@@ -431,9 +431,12 @@ func TestServedADoneKeyIsComposedAndGranted(t *testing.T) {
 		t.Fatal(err)
 	}
 	gk, _ := sdkdelivery.ControllerGrantKey("board", fp)
-	if _, err := grants.Get(ctx, gk); err != nil {
-		t.Errorf("grants.%s is not written: %v", gk, err)
-	}
+	// The take-in writes the grant after the compositions (composed_keys.go), so it is waited for, not read in the instant
+	// the composition shows: a loaded build node read it a moment early (issue 1945).
+	becomes(t, 10*time.Second, "grants."+gk+" written", func() bool {
+		_, err := grants.Get(ctx, gk)
+		return err == nil
+	})
 	if n := m.declarationsSent(t); n != 0 {
 		t.Errorf("%d declarations were sent", n)
 	}