Add roundtrip tests

Author: wooorm

package.json

@@ -42,6 +42,7 @@
   },
   "devDependencies": {
     "browserify": "^16.0.0",
+    "mdast-util-from-markdown": "^0.7.0",
     "nyc": "^15.0.0",
     "prettier": "^2.0.0",
     "remark-cli": "^8.0.0",

test.js

@@ -1,4 +1,5 @@
 var test = require('tape')
+var from = require('mdast-util-from-markdown')
 var to = require('.')
 
 test('mdast-util-to-markdown', function (t) {
@@ -2384,3 +2385,47 @@ test('escape', function (t) {
 
   t.end()
 })
+
+test('roundtrip', function (t) {
+  var doc = [
+    '> *   Lorem ipsum dolor sit amet',
+    '>',
+    '> *   consectetur adipisicing elit'
+  ].join('\n')
+
+  t.equal(to(from(doc)), doc, 'should roundtrip spread items in block quotes')
+
+  doc = [
+    '*   Lorem ipsum dolor sit amet',
+    '',
+    '    1.  consectetur adipisicing elit',
+    '',
+    '    2.  sed do eiusmod tempor incididunt'
+  ].join('\n')
+
+  t.equal(to(from(doc)), doc, 'should roundtrip spread items in sublists (1)')
+
+  doc = [
+    '*   1.  Lorem ipsum dolor sit amet',
+    '',
+    '    2.  consectetur adipisicing elit'
+  ].join('\n')
+
+  t.equal(to(from(doc)), doc, 'should roundtrip spread items in sublists (2)')
+
+  doc = [
+    '*   hello',
+    '    *   world',
+    '        how',
+    '',
+    '        are',
+    '        you',
+    '',
+    '    *   today',
+    '*   hi'
+  ].join('\n')
+
+  t.equal(to(from(doc)), doc, 'should roundtrip spread items in sublists (3)')
+
+  t.end()
+})