test: throw on warning when in tests

test/argsert.cjs

@@ -1,7 +1,7 @@
 /* global describe, it */
 const { argsert } = require('../build/index.cjs')
 const { checkOutput } = require('./helpers/utils.cjs')
-const { should } = require('chai')
+const { expect, should } = require('chai')
 
 should()
 
@@ -164,4 +164,15 @@ describe('Argsert', () => {
 
     o.warnings.length.should.equal(0)
   })
+
+  // See: https://github.com/yargs/yargs/issues/1666
+  it('should throw on warnings, when under test', () => {
+    function foo (...args) {
+      argsert('<*>', [].slice.call(args))
+    }
+
+    expect(() => {
+      foo('bar', undefined, undefined, 33)
+    }).to.throw();
+  })
 })

test/before.cjs

@@ -1,2 +1,6 @@
 'use strict'
 process.env.LC_ALL = 'en_US'
+// See: https://github.com/yargs/yargs/issues/1666
+console.warn = (message) => {
+  throw Error(message)
+}