third_party/web_platform_tests/XMLHttpRequest/FormData-append.html

<!doctype html>
<meta charset=utf-8>
<title>FormData.append</title>
<link rel=help href=https://xhr.spec.whatwg.org/#dom-formdata-append>
<script src=/resources/testharness.js></script>
<script src=/resources/testharnessreport.js></script>
<div id=log></div>
<script>
function test_formdata(creator, verifier, description) {
  async_test(description).step(function() {
    var fd = creator();
    var xhr = new XMLHttpRequest();
    xhr.onload = this.step_func(function() {
      verifier(xhr.responseText);
      this.done();
    });
    xhr.open("POST", "resources/upload.py");
    xhr.send(fd);
  })
}
test_formdata(function() {
  var fd = new FormData();
  fd.append("name", new String("value"));
  return fd;
}, function(data) {
  assert_equals(data, "name=value,\n");
}, "Passing a String object to FormData.append should work.");
</script>