First filter test

tests/src/Unit/Filters/TrimFilterTest.php

+<?php
+
+namespace Drupal\Tests\fapi_validation\Unit\Filters;
+
+use Drupal\Tests\UnitTestCase;
+use Drupal\fapi_validation\Plugin\FapiValidationFilter\TrimFilter;
+
+/**
+ * Tests generation of ice cream.
+ *
+ * @group fapi_validation
+ * @group fapi_validation_filters
+ */
+class TrimFilterTest extends UnitTestCase {
+
+  public function testValidString() {
+    $plugin = new TrimFilter;
+    $this->assertEquals('test', $plugin->filter('   test    '));
+  }
+
+}