diff --git a/test/downloadutils.mjs b/test/downloadutils.mjs
index ab002c5d3..682e916e3 100644
--- a/test/downloadutils.mjs
+++ b/test/downloadutils.mjs
@@ -13,7 +13,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/* eslint-disable no-var */
 
 import crypto from "crypto";
 import fs from "fs";
@@ -25,89 +24,73 @@ function rewriteWebArchiveUrl(url) {
   // Web Archive URLs need to be transformed to add `if_` after the ID.
   // Without this, an HTML page containing an iframe with the PDF file
   // will be served instead (issue 8920).
-  var webArchiveRegex =
+  const webArchiveRegex =
     /(^https?:\/\/web\.archive\.org\/web\/)(\d+)(\/https?:\/\/.+)/g;
-  var urlParts = webArchiveRegex.exec(url);
+  const urlParts = webArchiveRegex.exec(url);
   if (urlParts) {
-    return urlParts[1] + (urlParts[2] + "if_") + urlParts[3];
+    return `${urlParts[1]}${urlParts[2]}if_${urlParts[3]}`;
   }
   return url;
 }
 
-function downloadFile(file, url, callback, redirects) {
+function downloadFile(file, url, redirects = 0) {
   url = rewriteWebArchiveUrl(url);
+  const protocol = /^https:\/\//.test(url) ? https : http;
 
-  var protocol = /^https:\/\//.test(url) ? https : http;
-  protocol
-    .get(url, function (response) {
-      if (
-        response.statusCode === 301 ||
-        response.statusCode === 302 ||
-        response.statusCode === 307 ||
-        response.statusCode === 308
-      ) {
-        if (redirects > 10) {
-          callback("Too many redirects");
+  return new Promise((resolve, reject) => {
+    protocol
+      .get(url, async function (response) {
+        if ([301, 302, 307, 308].includes(response.statusCode)) {
+          if (redirects > 10) {
+            reject(new Error("Too many redirects"));
+            return;
+          }
+          const redirectTo = urlResolve(url, response.headers.location);
+          try {
+            await downloadFile(file, redirectTo, ++redirects);
+            resolve();
+          } catch (ex) {
+            reject(ex);
+          }
+          return;
         }
-        var redirectTo = response.headers.location;
-        redirectTo = urlResolve(url, redirectTo);
-        downloadFile(file, redirectTo, callback, (redirects || 0) + 1);
-        return;
-      }
 
-      if (response.statusCode !== 200) {
-        callback("HTTP " + response.statusCode);
-        return;
-      }
-      var stream = fs.createWriteStream(file);
-      stream.on("error", function (err) {
-        callback(err);
-      });
-      response.pipe(stream);
-      stream.on("finish", function () {
-        stream.end();
-        callback();
-      });
-    })
-    .on("error", function (err) {
-      callback(err);
-    });
+        if (response.statusCode !== 200) {
+          reject(new Error(`HTTP ${response.statusCode}`));
+          return;
+        }
+
+        const stream = fs.createWriteStream(file);
+        stream.on("error", error => reject(error));
+        stream.on("finish", () => {
+          stream.end();
+          resolve();
+        });
+        response.pipe(stream);
+      })
+      .on("error", error => reject(error));
+  });
 }
 
-function downloadManifestFiles(manifest, callback) {
-  function downloadNext() {
-    if (i >= links.length) {
-      callback();
-      return;
-    }
-    var file = links[i].file;
-    var url = links[i].url;
-    console.log("Downloading " + url + " to " + file + "...");
-    downloadFile(file, url, function (err) {
-      if (err) {
-        console.error("Error during downloading of " + url + ": " + err);
-        fs.writeFileSync(file, ""); // making it empty file
-        fs.writeFileSync(file + ".error", err);
-      }
-      i++;
-      downloadNext();
-    });
-  }
-
-  var links = manifest
-    .filter(function (item) {
-      return item.link && !fs.existsSync(item.file);
-    })
-    .map(function (item) {
-      var file = item.file;
-      var linkfile = file + ".link";
-      var url = fs.readFileSync(linkfile).toString();
+async function downloadManifestFiles(manifest) {
+  const links = manifest
+    .filter(item => item.link && !fs.existsSync(item.file))
+    .map(item => {
+      let url = fs.readFileSync(`${item.file}.link`).toString();
       url = url.replace(/\s+$/, "");
-      return { file, url };
+      return { file: item.file, url };
     });
 
-  var i = 0;
-  downloadNext();
+  for (const { file, url } of links) {
+    console.log(`Downloading ${url} to ${file}...`);
+    try {
+      await downloadFile(file, url);
+    } catch (ex) {
+      console.error(`Error during downloading of ${url}: ${ex}`);
+      fs.writeFileSync(file, ""); // making it empty file
+      fs.writeFileSync(`${file}.error`, ex);
+    }
+  }
 }
 
 function calculateMD5(file) {
diff --git a/test/test.mjs b/test/test.mjs
index 711adfa01..9595d63a7 100644
--- a/test/test.mjs
+++ b/test/test.mjs
@@ -268,7 +268,7 @@ function examineRefImages() {
   });
 }
 
-function startRefTest(masterMode, showRefImages) {
+async function startRefTest(masterMode, showRefImages) {
   function finalize() {
     stopServer();
     let numRuns = 0;
@@ -402,11 +402,10 @@ function startRefTest(masterMode, showRefImages) {
   if (!manifest) {
     return;
   }
-  if (options.noDownload) {
-    checkRefsTmp();
-  } else {
-    ensurePDFsDownloaded(checkRefsTmp);
+  if (!options.noDownload) {
+    await ensurePDFsDownloaded();
   }
+  checkRefsTmp();
 }
 
 function handleSessionTimeout(session) {
@@ -1071,47 +1070,43 @@ async function closeSession(browser) {
   }
 }
 
-function ensurePDFsDownloaded(callback) {
-  var manifest = getTestManifest();
-  downloadManifestFiles(manifest, async function () {
-    try {
-      await verifyManifestFiles(manifest);
-    } catch {
-      console.log(
-        "Unable to verify the checksum for the files that are " +
-          "used for testing."
-      );
-      console.log(
-        "Please re-download the files, or adjust the MD5 " +
-          "checksum in the manifest for the files listed above.\n"
-      );
-      if (options.strictVerify) {
-        process.exit(1);
-      }
+async function ensurePDFsDownloaded() {
+  const manifest = getTestManifest();
+  await downloadManifestFiles(manifest);
+  try {
+    await verifyManifestFiles(manifest);
+  } catch {
+    console.log(
+      "Unable to verify the checksum for the files that are " +
+        "used for testing."
+    );
+    console.log(
+      "Please re-download the files, or adjust the MD5 " +
+        "checksum in the manifest for the files listed above.\n"
+    );
+    if (options.strictVerify) {
+      process.exit(1);
     }
-    callback();
-  });
+  }
 }
 
-function main() {
+async function main() {
   if (options.statsFile) {
     stats = [];
   }
 
   if (options.downloadOnly) {
-    ensurePDFsDownloaded(function () {});
+    await ensurePDFsDownloaded();
   } else if (options.unitTest) {
     // Allows linked PDF files in unit-tests as well.
-    ensurePDFsDownloaded(function () {
-      startUnitTest("/test/unit/unit_test.html", "unit");
-    });
+    await ensurePDFsDownloaded();
+    startUnitTest("/test/unit/unit_test.html", "unit");
   } else if (options.fontTest) {
     startUnitTest("/test/font/font_test.html", "font");
   } else if (options.integration) {
     // Allows linked PDF files in integration-tests as well.
-    ensurePDFsDownloaded(function () {
-      startIntegrationTest();
-    });
+    await ensurePDFsDownloaded();
+    startIntegrationTest();
   } else {
     startRefTest(options.masterMode, options.reftest);
   }