feat(tests): update and improve tests

tests/src/flextype/core/FlextypHelperTest.php

@@ -1,19 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-use Flextype\Flextype;
-use Flextype\Content\Content;
-use Atomastic\Strings\Strings;
-
-test('test getVersion() method', function () {
-    $this->assertTrue(!Strings::create(flextype()->getVersion())->isEmpty());
-});
-
-test('test getInstance() method', function () {
-    $firstCall = flextype();
-    $secondCall = Flextype::getInstance();
-
-    $this->assertInstanceOf(Flextype::class, $firstCall);
-    $this->assertSame($firstCall, $secondCall);
-});

tests/src/flextype/core/HelpersTest.php

@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+use Flextype\Flextype;
+use Flextype\Content\Content;
+use Atomastic\Strings\Strings;
+use Slim\App;
+
+test('test flextype() helper', function () {
+    $this->assertSame(flextype(), Flextype::getInstance());
+});
+
+test('test app() helper', function () {
+    $this->assertSame(app(), Flextype::getInstance()->app());
+});