1 files changed, 76 insertions, 0 deletions
diff --git a/testing/web-platform/tests/css/mediaqueries/resources/matchmedia-utils.js b/testing/web-platform/tests/css/mediaqueries/resources/matchmedia-utils.js
new file mode 100644
index 0000000000..327e8f69fe
--- /dev/null
+++ b/testing/web-platform/tests/css/mediaqueries/resources/matchmedia-utils.js
@@ -0,0 +1,76 @@
+'use strict';
+
+function query_is_css_parseable(query) {
+  const style = document.createElement('style');
+  style.type = 'text/css';
+  document.head.appendChild(style);
+
+  const sheet = style.sheet;
+  try {
+    sheet.insertRule("@media " + query + "{}", 0);
+    return sheet.cssRules.length == 1 &&
+        sheet.cssRules[0].media.mediaText != "not all";
+  } finally {
+    while (sheet.cssRules.length)
+      sheet.deleteRule(0);
+    style.remove();
+  }
+}
+
+function query_should_be_css_parseable(query) {
+  test(() => {
+    assert_true(query_is_css_parseable(query));
+  }, "Should be parseable in a CSS stylesheet: '" + query + "'");
+}
+
+function query_should_not_be_css_parseable(query) {
+  test(() => {
+    assert_false(query_is_css_parseable(query));
+  }, "Should not be parseable in a CSS stylesheet: '" + query + "'");
+}
+
+function query_is_js_parseable(query) {
+  // We cannot rely on whether a given feature is on or off, so only check the
+  // 'media' member of the result.
+  const match = window.matchMedia(query);
+  return match.media == query;
+}
+
+function query_should_be_js_parseable(query) {
+  test(() => {
+    assert_true(query_is_js_parseable(query));
+  }, "Should be parseable in JS: '" + query + "'");
+}
+
+function query_should_not_be_js_parseable(query) {
+  test(() => {
+    assert_false(query_is_js_parseable(query));
+  }, "Should not be parseable in JS: '" + query + "'");
+}
+
+function query_is_known(query) {
+  return window.matchMedia(`${query}, not all and ${query}`).matches;
+}
+
+function query_is_unknown(query) {
+  return !window.matchMedia(`${query}, not all and ${query}`).matches;
+}
+
+function query_should_be_known(query) {
+  test(() => {
+    assert_true(query_is_js_parseable(query), "Can parse with JS");
+    assert_true(query_is_css_parseable(query), "Can parse with CSS");
+    assert_true(query_is_known(query));
+  }, "Should be known: '" + query + "'");
+}
+
+function query_should_be_unknown(query) {
+  test(() => {
+    assert_true(query_is_js_parseable(query), "Can parse with JS");
+    assert_true(query_is_css_parseable(query), "Can parse with CSS");
+  }, "Should be parseable: '" + query + "'");
+
+  test(() => {
+    assert_true(query_is_unknown(query));
+  }, "Should be unknown: '" + query + "'");
+}