Halkyon's shared packages

A pub workspace of the Dart packages Halkyon's apps share: halkyon_ui,
Halkyon's look (the theme, fonts, layout and shared widgets, with texts
in English and German), halkyon_core's low-level primitives and
halkyon_interop's cross-app contracts. Dart 3.13 with LeanCode's lints,
configured once at the root; apps take a package by git, pinned to a
signed commit.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

packages/halkyon_core/test/halkyon_core_test.dart

@@ -0,0 +1,52 @@
+import 'package:halkyon_core/halkyon_core.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('generateUuid', () {
+    test('produces a non-empty string', () {
+      expect(generateUuid(), isNotEmpty);
+    });
+
+    test('produces a valid v4 UUID format', () {
+      // v4 UUID: 8-4-4-4-12 hex characters, with version 4 in the third group.
+      final uuid = generateUuid();
+      expect(
+        uuid,
+        matches(
+          RegExp(
+            r'^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$',
+          ),
+        ),
+      );
+    });
+
+    test('produces different values on successive calls', () {
+      final a = generateUuid();
+      final b = generateUuid();
+      expect(a, isNot(equals(b)));
+    });
+  });
+
+  group('ConsoleLogger', () {
+    test('can be instantiated as const', () {
+      const logger = ConsoleLogger();
+      expect(logger, isA<Logger>());
+    });
+
+    // Note: we don't test that ConsoleLogger actually prints, because
+    // capturing stdout in tests is fragile and the implementation is trivial.
+    // If we add structured logging later, we'll test that more carefully.
+  });
+
+  group('HalkyonException', () {
+    test('is implementable', () {
+      final ex = _TestException('boom');
+      expect(ex, isA<HalkyonException>());
+      expect(ex, isA<Exception>());
+      expect(ex.message, equals('boom'));
+    });
+  });
+}
+
+class _TestException(@override final String message)
+    implements HalkyonException;