diff --git a/tests/phpunit/tests/general/allowedTags.php b/tests/phpunit/tests/general/allowedTags.php
new file mode 100644
index 0000000000000..47c415d5e79c4
--- /dev/null
+++ b/tests/phpunit/tests/general/allowedTags.php
@@ -0,0 +1,75 @@
+<?php
+
+/**
+ * Tests for the `allowed_tags()` function.
+ *
+ * @group general
+ * @group formatting
+ *
+ * @covers ::allowed_tags
+ */
+class Tests_General_AllowedTags extends WP_UnitTestCase {
+
+	/**
+	 * Original allowed tags.
+	 *
+	 * @var array
+	 */
+	private $original_allowedtags;
+
+	public function set_up() {
+		parent::set_up();
+		global $allowedtags;
+		$this->original_allowedtags = $allowedtags;
+	}
+
+	public function tear_down() {
+		global $allowedtags;
+		$allowedtags = $this->original_allowedtags;
+		parent::tear_down();
+	}
+
+	/**
+	 * Tests that allowed_tags() returns encoded string of default allowed tags.
+	 *
+	 * @ticket 65819
+	 */
+	public function test_allowed_tags_default() {
+		$expected = '&lt;a href=&quot;&quot; title=&quot;&quot;&gt; &lt;abbr title=&quot;&quot;&gt; &lt;acronym title=&quot;&quot;&gt; &lt;b&gt; &lt;blockquote cite=&quot;&quot;&gt; &lt;cite&gt; &lt;code&gt; &lt;del datetime=&quot;&quot;&gt; &lt;em&gt; &lt;i&gt; &lt;q cite=&quot;&quot;&gt; &lt;s&gt; &lt;strike&gt; &lt;strong&gt; ';
+		$this->assertSame( $expected, allowed_tags() );
+	}
+
+	/**
+	 * Tests that allowed_tags() formats custom tags and attributes correctly.
+	 *
+	 * @ticket 65819
+	 */
+	public function test_allowed_tags_custom() {
+		global $allowedtags;
+
+		$allowedtags = array(
+			'em'     => array(),
+			'strong' => array( 'class' => true ),
+			'span'   => array(
+				'class' => true,
+				'id'    => true,
+			),
+		);
+
+		$expected = '&lt;em&gt; &lt;strong class=&quot;&quot;&gt; &lt;span class=&quot;&quot; id=&quot;&quot;&gt; ';
+		$this->assertSame( $expected, allowed_tags() );
+	}
+
+	/**
+	 * Tests that allowed_tags() returns an empty string when allowedtags is empty.
+	 *
+	 * @ticket 65819
+	 */
+	public function test_allowed_tags_empty() {
+		global $allowedtags;
+
+		$allowedtags = array();
+
+		$this->assertSame( '', allowed_tags() );
+	}
+}