test: add case for unknown command

Author: jamesgeorge007

e2e/index.js

@@ -20,3 +20,8 @@ test('shows help with -h flag', matchSnapshot, '-h')
 test('shows help with --help flag', matchSnapshot, '--help')
 test('shows version information with -v flag', matchSnapshot, '-v')
 test('shows version information with --version flag', matchSnapshot, '--version')
+
+test('rejects promise due to error on passing in an unknown command', async t => {
+  const {stderr} = await execa(rootCommand, ['junkcmd'], {reject: false})
+  t.snapshot(stderr)
+})

e2e/index.js.md

@@ -89,3 +89,27 @@ Generated by [AVA](https://ava.li).
     docsify-cli version:␊
       4.4.0␊
     `
+
+## rejects promise due to error on passing in an unknown command
+
+> Snapshot 1
+
+    `Usage: docsify <init|serve> <path>␊
+    ␊
+    Commands:␊
+      docsify init [path]   Creates new docs␊
+      docsify serve [path]  Run local server to preview site.␊
+      docsify start <path>  Server for SSR␊
+    ␊
+    Global Options␊
+      --help, -h     Show help                                             [boolean]␊
+      --version, -v  Show version number                                   [boolean]␊
+    ␊
+    Documentation:␊
+      https://docsifyjs.github.io/docsify␊
+      https://docsifyjs.github.io/docsify-cli␊
+    ␊
+    Development:␊
+      https://github.com/docsifyjs/docsify-cli/blob/master/CONTRIBUTING.md␊
+    ␊
+    Unknown argument: junkcmd`