add marks empty schema test

packages/slate-schema/test/validations/marks/invalid-empty.js

@@ -0,0 +1,27 @@
+/** @jsx jsx */
+
+import { jsx } from 'slate-hyperscript'
+
+export const schema = [
+  {
+    for: 'node',
+    match: 'element',
+    validate: {
+      marks: [],
+    },
+  },
+]
+
+export const input = (
+  <editor>
+    <element>
+      <mark a>text</mark>
+    </element>
+  </editor>
+)
+
+export const output = (
+  <editor>
+    <element>text</element>
+  </editor>
+)