diff --git a/tests/phpunit/tests/admin/includes/misc/updateRecentlyEdited.php b/tests/phpunit/tests/admin/includes/misc/updateRecentlyEdited.php
new file mode 100644
index 0000000000000..ed02efd2dec78
--- /dev/null
+++ b/tests/phpunit/tests/admin/includes/misc/updateRecentlyEdited.php
@@ -0,0 +1,145 @@
+<?php
+/**
+ * Tests for the update_recently_edited() function.
+ *
+ * @group admin
+ * @group admin-includes
+ * @covers ::update_recently_edited
+ */
+class Tests_update_recently_edited extends WP_UnitTestCase {
+
+	/**
+	 * Tests that update_recently_edited() adds a new file to the list.
+	 *
+	 * @ticket 65174
+	 */
+	public function test_update_recently_edited_adds_new_file() {
+		$file = 'test-file.php';
+		update_recently_edited( $file );
+
+		$this->assertSame( array( $file ), array_filter( array_values( get_option( 'recently_edited' ) ) ) );
+	}
+
+	/**
+	 * Tests that update_recently_edited() maintains a maximum of 5 files.
+	 *
+	 * @ticket 65174
+	 */
+	public function test_update_recently_edited_maintains_max_5_files() {
+		$files = array(
+			'file1.php',
+			'file2.php',
+			'file3.php',
+			'file4.php',
+			'file5.php',
+		);
+
+		foreach ( $files as $file ) {
+			update_recently_edited( $file );
+		}
+
+		$this->assertSame( array_reverse( $files ), array_filter( array_values( get_option( 'recently_edited' ) ) ) );
+
+		$new_file = 'file6.php';
+		update_recently_edited( $new_file );
+
+		$expected = array(
+			'file6.php',
+			'file5.php',
+			'file4.php',
+			'file3.php',
+			'file2.php',
+		);
+
+		$this->assertSame( $expected, array_filter( array_values( get_option( 'recently_edited' ) ) ) );
+	}
+
+	/**
+	 * Tests that update_recently_edited() moves an existing file to the top.
+	 *
+	 * @ticket 65174
+	 */
+	public function test_update_recently_edited_moves_existing_file_to_top() {
+		$files = array(
+			'file1.php',
+			'file2.php',
+			'file3.php',
+		);
+
+		foreach ( $files as $file ) {
+			update_recently_edited( $file );
+		}
+
+		// Current state: array( 'file3.php', 'file2.php', 'file1.php' )
+		update_recently_edited( 'file1.php' );
+
+		$expected = array(
+			'file1.php',
+			'file3.php',
+			'file2.php',
+		);
+
+		$this->assertSame( $expected, array_filter( array_values( get_option( 'recently_edited' ) ) ) );
+	}
+
+	/**
+	 * Tests update_recently_edited() with various inputs using a data provider.
+	 *
+	 * @ticket 65174
+	 * @dataProvider data_update_recently_edited
+	 *
+	 * @param array  $initial_option The initial 'recently_edited' option.
+	 * @param string $new_file       The new file to add.
+	 * @param array  $expected       The expected 'recently_edited' option.
+	 */
+	public function test_update_recently_edited_cases( $initial_option, $new_file, $expected ) {
+		if ( false !== $initial_option ) {
+			update_option( 'recently_edited', $initial_option );
+		} else {
+			delete_option( 'recently_edited' );
+		}
+
+		update_recently_edited( $new_file );
+
+		$this->assertSame( $expected, array_filter( array_values( get_option( 'recently_edited' ) ) ) );
+	}
+
+	/**
+	 * Data provider for test_update_recently_edited_cases.
+	 *
+	 * @return array<string, array{
+	 *     initial_option: array<int, string>|false,
+	 *     new_file:       string,
+	 *     expected:       array<int, string>,
+	 * }>
+	 */
+	public function data_update_recently_edited(): array {
+		return array(
+			'empty_option'           => array(
+				'initial_option' => false,
+				'new_file'       => 'new.php',
+				'expected'       => array( 'new.php' ),
+			),
+			'one_item'               => array(
+				'initial_option' => array( 'old.php' ),
+				'new_file'       => 'new.php',
+				'expected'       => array( 'new.php', 'old.php' ),
+			),
+			'duplicate_item'         => array(
+				'initial_option' => array( 'old.php', 'new.php' ),
+				'new_file'       => 'new.php',
+				'expected'       => array( 'new.php', 'old.php' ),
+			),
+			'max_items_at_limit'     => array(
+				'initial_option' => array( '1.php', '2.php', '3.php', '4.php' ),
+				'new_file'       => '5.php',
+				'expected'       => array( '5.php', '1.php', '2.php', '3.php', '4.php' ),
+			),
+			'max_items_exceed_limit' => array(
+				'initial_option' => array( '1.php', '2.php', '3.php', '4.php', '5.php' ),
+				'new_file'       => '6.php',
+				'expected'       => array( '6.php', '1.php', '2.php', '3.php', '4.php' ),
+			),
+		);
+	}
+}