test: create tests for AvatarThemeData

packages/stream_chat_flutter/lib/src/theme/avatar_theme.dart

@@ -56,7 +56,7 @@ class AvatarTheme extends InheritedTheme {
 /// the default style for [UserAvatar]s below the overall [StreamChatTheme].
 class AvatarThemeData with Diagnosticable {
   /// Creates an [AvatarThemeData].
-  AvatarThemeData({
+  const AvatarThemeData({
     BoxConstraints? constraints,
     BorderRadius? borderRadius,
   })  : _constraints = constraints,

packages/stream_chat_flutter/test/src/avatar_theme_test.dart

@@ -0,0 +1,50 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:stream_chat_flutter/stream_chat_flutter.dart';
+
+void main() {
+  test('AvatarThemeData copyWith, ==, hashCode basics', () {
+    expect(const AvatarThemeData(), const AvatarThemeData().copyWith());
+    expect(const AvatarThemeData().hashCode,
+        const AvatarThemeData().copyWith().hashCode);
+  });
+
+  group('AvatarThemeData lerps correctly', () {
+    test('Lerp completely', () {
+      expect(
+          const AvatarThemeData()
+              .lerp(_avatarThemeDataControl1, _avatarThemeDataControl2, 1),
+          _avatarThemeDataControl2);
+    });
+
+    test('Lerp halfway', () {
+      expect(
+          const AvatarThemeData()
+              .lerp(_avatarThemeDataControl1, _avatarThemeDataControl2, 0.5),
+          _avatarThemeDataControlMidLerp);
+    });
+  });
+
+  test('Merging two AvatarThemeData results in the latter', () {
+    expect(_avatarThemeDataControl1.merge(_avatarThemeDataControl2),
+        _avatarThemeDataControl2);
+  });
+}
+
+const _avatarThemeDataControl1 = AvatarThemeData();
+
+final _avatarThemeDataControlMidLerp = AvatarThemeData(
+  borderRadius: BorderRadius.circular(16),
+  constraints: const BoxConstraints.tightFor(
+    height: 33,
+    width: 33,
+  ),
+);
+
+final _avatarThemeDataControl2 = AvatarThemeData(
+  borderRadius: BorderRadius.circular(12),
+  constraints: const BoxConstraints.tightFor(
+    height: 34,
+    width: 34,
+  ),
+);