lookupFiles(): fix regression and glob

lib/utils.js

@@ -563,35 +563,38 @@ function isHiddenOnUnix(pathname) {
  * @public
  * @memberof Mocha.utils
  * @param {string} filepath - Base path to start searching from.
- * @param {string[]} extensions - File extensions to look for.
- * @param {boolean} recursive - Whether to recurse into subdirectories.
+ * @param {string[]} [extensions=[]] - File extensions to look for.
+ * @param {boolean} [recursive=false] - Whether to recurse into subdirectories.
  * @return {string[]} An array of paths.
  * @throws {Error} if no files match pattern.
  * @throws {TypeError} if `filepath` is directory and `extensions` not provided.
  */
 exports.lookupFiles = function lookupFiles(filepath, extensions, recursive) {
   extensions = extensions || [];
+  recursive = recursive || false;
   var files = [];
   var stat;
 
   if (!fs.existsSync(filepath)) {
-    // check all extensions
-    extensions.forEach(function(ext) {
-      if (fs.existsSync(filepath + '.' + ext)) {
-        files.push(filepath + '.' + ext);
-      }
-    });
-    if (!files.length) {
+    // Check all extensions, using first match found (if any)
+    if (
+      !extensions.some(function(ext) {
+        if (fs.existsSync(filepath + '.' + ext)) {
+          filepath += '.' + ext;
+          return true;
+        }
+      })
+    ) {
       // Handle glob
-      files = glob.sync(filepath);
+      files = glob.sync(filepath, {nodir: true});
       if (!files.length) {
         throw createNoFilesMatchPatternError(
           'Cannot find any files matching pattern ' + exports.dQuote(filepath),
           filepath
         );
       }
+      return files;
     }
-    return files;
   }
 
   // Handle file