diff --git a/TypeSystem/flow-analysis/type_of_interest_A03_t01.dart b/TypeSystem/flow-analysis/type_of_interest_A03_t01.dart
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+++ b/TypeSystem/flow-analysis/type_of_interest_A03_t01.dart
@@ -0,0 +1,39 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// @assertion We say that at type `T` is a type of interest for a variable `x`
+/// in a set of tested types `tested` if `tested` contains a type `S` such that
+/// `T` is `S`, or `T` is `NonNull(S)`.
+///
+/// @description Checks that the list of types of interests always contains
+/// `NonNull(declared)`.
+/// @author sgrekhov22@gmail.com
+
+import '../../Utils/static_type_helper.dart';
+
+test1(Object? o) {
+  o = Object();
+  o.expectStaticType<Exactly<Object>>();
+}
+
+test2(Object? o) {
+  o = 42;
+  // `int` is not a type of interest for `o` but `int <: Object` therefore `o`
+  // is promoted to `Object`
+  o.expectStaticType<Exactly<Object>>();
+}
+
+test3(Pattern? o) {
+  o = "";
+  o.expectStaticType<Exactly<Pattern>>();
+}
+
+main() {
+  test1("");
+  test1(null);
+  test2("");
+  test2(null);
+  test3("");
+  test3(null);
+}