1 files changed, 69 insertions, 0 deletions
diff --git a/devtools/client/shared/test/browser_theme_switching.js b/devtools/client/shared/test/browser_theme_switching.js
new file mode 100644
index 0000000000..34e0a9b416
--- /dev/null
+++ b/devtools/client/shared/test/browser_theme_switching.js
@@ -0,0 +1,69 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async function () {
+  // For some reason, mochitest spawn a very special default tab,
+  // whose WindowGlobal is still the initial about:blank document.
+  // This seems to be specific to mochitest, this doesn't reproduce
+  // in regular firefox run. Even having about:blank as home page,
+  // force loading another final about:blank document (which isn't the initial one)
+  //
+  // To workaround this, force opening a dedicated test tab
+  const tab = await addTab("data:text/html;charset=utf-8,Test page");
+
+  const toolbox = await gDevTools.showToolboxForTab(tab);
+  const doc = toolbox.doc;
+  const root = doc.documentElement;
+
+  const platform = root.getAttribute("platform");
+  const expectedPlatform = getPlatform();
+  is(platform, expectedPlatform, ":root[platform] is correct");
+
+  const theme = Services.prefs.getCharPref("devtools.theme");
+  const className = "theme-" + theme;
+  ok(
+    root.classList.contains(className),
+    ":root has " + className + " class (current theme)"
+  );
+
+  // Convert the xpath result into an array of strings
+  // like `href="{URL}" type="text/css"`
+  const sheetsIterator = doc.evaluate(
+    "processing-instruction('xml-stylesheet')",
+    doc,
+    null,
+    XPathResult.ANY_TYPE,
+    null
+  );
+  const sheetsInDOM = [];
+
+  /* eslint-disable no-cond-assign */
+  let sheet;
+  while ((sheet = sheetsIterator.iterateNext())) {
+    sheetsInDOM.push(sheet.data);
+  }
+  /* eslint-enable no-cond-assign */
+
+  const sheetsFromTheme = gDevTools.getThemeDefinition(theme).stylesheets;
+  info("Checking for existence of " + sheetsInDOM.length + " sheets");
+  for (const themeSheet of sheetsFromTheme) {
+    ok(
+      sheetsInDOM.some(s => s.includes(themeSheet)),
+      "There is a stylesheet for " + themeSheet
+    );
+  }
+
+  await toolbox.destroy();
+});
+
+function getPlatform() {
+  const { OS } = Services.appinfo;
+  if (OS == "WINNT") {
+    return "win";
+  } else if (OS == "Darwin") {
+    return "mac";
+  }
+  return "linux";
+}