diff --git a/lib/cli/collect-files.js b/lib/cli/collect-files.js
index f4fc10ba31..ad4699ec6e 100644
--- a/lib/cli/collect-files.js
+++ b/lib/cli/collect-files.js
@@ -8,23 +8,17 @@ const utils = require('../utils');
 
 /**
  * Smash together an array of test files in the correct order
- * @param {Object} [opts] - Options
- * @param {string[]} [opts.extension] - File extensions to use
- * @param {string[]} [opts.spec] - Files, dirs, globs to run
- * @param {string[]} [opts.ignore] - Files, dirs, globs to ignore
- * @param {boolean} [opts.recursive=false] - Find files recursively
- * @param {boolean} [opts.sort=false] - Sort test files
+ * @param {Object} opts - Options
+ * @param {string[]} opts.extension - File extensions to use
+ * @param {string[]} opts.spec - Files, dirs, globs to run
+ * @param {string[]} opts.ignore - Files, dirs, globs to ignore
+ * @param {string[]} opts.file - List of additional files to include
+ * @param {boolean} opts.recursive - Find files recursively
+ * @param {boolean} opts.sort - Sort test files
  * @returns {string[]} List of files to test
  * @private
  */
-module.exports = ({
-  ignore = [],
-  extension = [],
-  file = [],
-  recursive = false,
-  sort = false,
-  spec = []
-} = {}) => {
+module.exports = ({ignore, extension, file, recursive, sort, spec} = {}) => {
   let files = [];
   const unmatched = [];
   spec.forEach(arg => {
diff --git a/lib/cli/run-helpers.js b/lib/cli/run-helpers.js
index 791b88a8c5..26b44c0070 100644
--- a/lib/cli/run-helpers.js
+++ b/lib/cli/run-helpers.js
@@ -96,14 +96,16 @@ exports.handleRequires = (requires = []) => {
  * @param {Mocha} mocha - Mocha instance
  * @param {Options} [opts] - Command line options
  * @param {boolean} [opts.exit] - Whether or not to force-exit after tests are complete
+ * @param {Object} fileCollectParams - Parameters that control test
+ *   file collection. See `lib/cli/collect-files.js`.
  * @returns {Runner}
  * @private
  */
-exports.singleRun = (mocha, options) => {
-  const files = collectFiles(options);
+exports.singleRun = (mocha, {exit}, fileCollectParams) => {
+  const files = collectFiles(fileCollectParams);
   debug('running tests with files', files);
   mocha.files = files;
-  return mocha.run(options.exit ? exitMocha : exitMochaLater);
+  return mocha.run(exit ? exitMocha : exitMochaLater);
 };
 
 /**
@@ -113,20 +115,32 @@ exports.singleRun = (mocha, options) => {
  * @private
  */
 exports.runMocha = (mocha, options) => {
-  options = Object.assign(
-    {
-      watch: false,
-      extension: [],
-      grep: '',
-      ui: 'bdd',
-      exit: false
-    },
-    options
-  );
-  if (options.watch) {
-    watchRun(mocha, options);
+  const {
+    watch = false,
+    extension = [],
+    grep = '',
+    ui = 'bdd',
+    exit = false,
+    ignore = [],
+    file = [],
+    recursive = false,
+    sort = false,
+    spec = []
+  } = options;
+
+  const fileCollectParams = {
+    ignore,
+    extension,
+    file,
+    recursive,
+    sort,
+    spec
+  };
+
+  if (watch) {
+    watchRun(mocha, {exit}, fileCollectParams);
   } else {
-    exports.singleRun(mocha, options);
+    exports.singleRun(mocha, {ui, grep}, fileCollectParams);
   }
 };
 
diff --git a/lib/cli/watch-run.js b/lib/cli/watch-run.js
index 6a77e09937..a2264c812c 100644
--- a/lib/cli/watch-run.js
+++ b/lib/cli/watch-run.js
@@ -15,12 +15,17 @@ const collectFiles = require('./collect-files');
 /**
  * Run Mocha in "watch" mode
  * @param {Mocha} mocha - Mocha instance
- * @param {Object} [opts] - Command line options
+ * @param {Object} opts - Options
+ * @param {string|RegExp} opts.grep - Grep for test titles
+ * @param {string} opts.ui - User interface
+ * @param {Object} fileCollectParams - Parameters that control test
+ *   file collection. See `lib/cli/collect-files.js`.
+ * @param {string[]} fileCollectParams.extension - List of extensions to watch
  * @private
  */
-module.exports = (mocha, options) => {
+module.exports = (mocha, options, fileCollectParams) => {
   let runner;
-  const files = collectFiles(options);
+  const files = collectFiles(fileCollectParams);
 
   console.log();
   hideCursor();
@@ -32,7 +37,7 @@ module.exports = (mocha, options) => {
     process.exit(128 + 2);
   });
 
-  const watchFiles = utils.files(process.cwd(), options.extension);
+  const watchFiles = utils.files(process.cwd(), fileCollectParams.extension);
   let runAgain = false;
 
   const loadAndRun = () => {