Fix tests

Author: ehmicky

src/options/classes.js

@@ -18,7 +18,7 @@ export const applyClassesOpts = ({ name }, opts = {}) => {
   return { ...optsA, ...removeUndefined(classesOpts) }
 }
 
-const validateObject = (value, optName) => {
+export const validateObject = (value, optName) => {
   if (!isPlainObj(value)) {
     throw new Error(`"${optName}" must be a plain object: ${value}`)
   }

src/options/validate.js

@@ -4,14 +4,12 @@ import isPlainObj from 'is-plain-obj'
 import { validateExitCode } from '../exit.js'
 import { validateTimeout } from '../timeout.js'
 
-import { applyClassesOpts } from './classes.js'
+import { applyClassesOpts, validateObject } from './classes.js'
 
 // Validate option values.
 // This is exported, although not documented.
-export const validateOptions = (opts) => {
-  if (!isPlainObj(opts)) {
-    return
-  }
+export const validateOptions = (opts = {}) => {
+  validateObject(opts, 'options')
 
   const { classes } = opts
   const names =