chromium/third_party/blink/web_tests/external/wpt/html/semantics/forms/the-input-element/files.html

<!doctype html>
<meta charset=utf-8>
<title>HTMLInputElement#files</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<div id=log></div>
<script>
var types = [
  "hidden",
  "text",
  "search",
  "tel",
  "url",
  "email",
  "password",
  "date",
  "month",
  "week",
  "time",
  "datetime-local",
  "number",
  "range",
  "color",
  "checkbox",
  "radio",
  "submit",
  "image",
  "reset",
  "button",
];

types.forEach(function(type) {
  test(function() {
    const input = document.createElement("input"),
          input2 = document.createElement("input");
    input.type = type;
    input2.type = "file";
    assert_equals(input.files, null, "files should be null");

    input.files = input2.files;
    assert_equals(input.files, null, "files should remain null as it cannot be set when it does not apply");
  }, "files for input type=" + type);
});

test(function() {
  var input = document.createElement("input");
  input.type = "file";
  assert_not_equals(input.files, null);
  assert_true(input.files instanceof FileList, "files should be a FileList");
  var files = input.files;
  assert_equals(input.files, files, "files should return the same object");
}, "files for input type=file");

test(() => {
  const i1 = document.createElement("input"),
        i2 = document.createElement("input");
  i1.type = "file";
  i2.type = "file";

  const files = i2.files;
  i1.files = i2.files;
  assert_equals(i1.files, files, "FileList should not be copied");
  assert_equals(i2.files, files, "FileList can be shared across input elements");

  i1.files = null;
  assert_equals(i1.files, files, "files cannot be set to null");

  assert_throws_js(TypeError, () => i1.files = [], "files cannot be set to an array");
  assert_throws_js(TypeError, () => i1.files = [new File([], "x")], "files cannot be set to an array (even when it contains File objects)");
}, "setting <input type=file>.files");

test(() => {
  const i = document.createElement("input");
  i.type = "file";

  let dt = new DataTransfer();

  const files = dt.files;
  i.files = files;
  assert_equals(i.files, files, "FileList should not be copied");
  assert_equals(dt.files, files, "FileList can be shared across input / DataTransfer");
}, "setting <input type=file>.files from DataTransfer");
</script>