diff --git a/tests/phpunit/tests/functions/wpIsWritable.php b/tests/phpunit/tests/functions/wpIsWritable.php
new file mode 100644
index 0000000000000..f2bdb2b013c3d
--- /dev/null
+++ b/tests/phpunit/tests/functions/wpIsWritable.php
@@ -0,0 +1,40 @@
+<?php
+
+/**
+ * Tests for wp_is_writable().
+ *
+ * @group functions
+ *
+ * @covers ::wp_is_writable
+ */
+class Tests_Functions_wpIsWritable extends WP_UnitTestCase {
+
+	/**
+	 * @ticket 65819
+	 */
+	public function test_returns_true_for_writable_directory() {
+		$this->assertTrue( wp_is_writable( get_temp_dir() ) );
+	}
+
+	/**
+	 * @ticket 65819
+	 */
+	public function test_returns_false_for_path_with_missing_parent() {
+		// Parent directory must not exist so Windows win_is_writable() cannot create the file.
+		$path = trailingslashit( get_temp_dir() ) . 'wp-is-writable-missing-' . wp_generate_password( 8, false ) . '/file.txt';
+
+		$this->assertFalse( wp_is_writable( $path ) );
+	}
+
+	/**
+	 * @ticket 65819
+	 */
+	public function test_returns_true_for_writable_file() {
+		$file = wp_tempnam( 'wp-is-writable-' );
+
+		$this->assertNotFalse( $file );
+		$this->assertTrue( wp_is_writable( $file ) );
+
+		unlink( $file );
+	}
+}