Add tests for avoid-unrelated-type-assertions rule

lint_test/analysis_options.yaml

@@ -18,3 +18,4 @@ custom_lint:
     - double-literal-format
     - avoid-unnecessary-type-assertions
     - avoid-unnecessary-type-casts
+    - avoid-unrelated-type-assertions

lint_test/avoid_unrelated_type_assertions_test.dart

@@ -0,0 +1,33 @@
+// ignore_for_file: prefer_const_declarations
+// ignore_for_file: unnecessary_nullable_for_final_variable_declarations
+// ignore_for_file: unused_local_variable
+
+/// Check the `avoid-unrelated-type-assertions` rule
+class Foo {}
+
+class Bar {}
+
+class ChildFoo extends Foo {}
+
+void fun() {
+  final testString = '';
+  final testList = [1, 2, 3];
+  final testMap = {'A': 'B'};
+  final Foo foo = Foo();
+  final childFoo = ChildFoo();
+
+  // expect_lint: avoid-unrelated-type-assertions
+  final result = testString is int;
+
+  // expect_lint: avoid-unrelated-type-assertions
+  final result2 = testList is List<String>;
+
+  // expect_lint: avoid-unrelated-type-assertions
+  final result3 = foo is Bar;
+
+  // expect_lint: avoid-unrelated-type-assertions
+  final result4 = childFoo is Bar;
+
+  // expect_lint: avoid-unrelated-type-assertions
+  final result5 = testMap['A'] is double;
+}