diff --git a/tests/phpunit/tests/functions/wpCheckFiletype.php b/tests/phpunit/tests/functions/wpCheckFiletype.php
new file mode 100644
index 0000000000..ad947c628b
--- /dev/null
+++ b/tests/phpunit/tests/functions/wpCheckFiletype.php
@@ -0,0 +1,111 @@
+<?php
+
+/**
+ * Tests for wp_check_filetype().
+ *
+ * @group functions.php
+ * @group upload
+ *
+ * @covers ::wp_check_filetype
+ */
+class Tests_Functions_WpCheckFiletype extends WP_UnitTestCase {
+
+	/**
+	 * Tests that wp_check_filetype() returns the correct extension and MIME type.
+	 *
+	 * @ticket 57151
+	 *
+	 * @dataProvider data_wp_check_filetype
+	 *
+	 * @param string     $filename   The filename to check.
+	 * @param array|null $mimes      An array of MIME types, or null.
+	 * @param array      $expected   An array containing the expected extension and MIME type.
+	 */
+	public function test_wp_check_filetype( $filename, $mimes, $expected ) {
+		$this->assertSame( $expected, wp_check_filetype( $filename, $mimes ) );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return[]
+	 */
+	public function data_wp_check_filetype() {
+		return array(
+			'.jpg filename and default allowed'       => array(
+				'filename' => 'canola.jpg',
+				'mimes'    => null,
+				'expected' => array(
+					'ext'  => 'jpg',
+					'type' => 'image/jpeg',
+				),
+			),
+			'.jpg filename and jpg|jpeg|jpe'          => array(
+				'filename' => 'canola.jpg',
+				'mimes'    => array(
+					'jpg|jpeg|jpe' => 'image/jpeg',
+					'gif'          => 'image/gif',
+				),
+				'expected' => array(
+					'ext'  => 'jpg',
+					'type' => 'image/jpeg',
+				),
+			),
+			'.jpeg filename and jpg|jpeg|jpe'         => array(
+				'filename' => 'canola.jpeg',
+				'mimes'    => array(
+					'jpg|jpeg|jpe' => 'image/jpeg',
+					'gif'          => 'image/gif',
+				),
+				'expected' => array(
+					'ext'  => 'jpeg',
+					'type' => 'image/jpeg',
+				),
+			),
+			'.jpe filename and jpg|jpeg|jpe'          => array(
+				'filename' => 'canola.jpe',
+				'mimes'    => array(
+					'jpg|jpeg|jpe' => 'image/jpeg',
+					'gif'          => 'image/gif',
+				),
+				'expected' => array(
+					'ext'  => 'jpe',
+					'type' => 'image/jpeg',
+				),
+			),
+			'uppercase filename and jpg|jpeg|jpe'     => array(
+				'filename' => 'canola.JPG',
+				'mimes'    => array(
+					'jpg|jpeg|jpe' => 'image/jpeg',
+					'gif'          => 'image/gif',
+				),
+				'expected' => array(
+					'ext'  => 'JPG',
+					'type' => 'image/jpeg',
+				),
+			),
+			'.XXX filename and no matching MIME type' => array(
+				'filename' => 'canola.XXX',
+				'mimes'    => array(
+					'jpg|jpeg|jpe' => 'image/jpeg',
+					'gif'          => 'image/gif',
+				),
+				'expected' => array(
+					'ext'  => false,
+					'type' => false,
+				),
+			),
+			'.jpg filename but only gif allowed'      => array(
+				'filename' => 'canola.jpg',
+				'mimes'    => array(
+					'gif' => 'image/gif',
+				),
+				'expected' => array(
+					'ext'  => false,
+					'type' => false,
+				),
+			),
+
+		);
+	}
+}