Write the same plain markdown for documents the editor holds equal: normalize the reduction's input again, naming a refusal by the caller's document

src/conformance/adf-property.test.ts

@@ -8,6 +8,7 @@ import { adfToMarkdown } from '../markdown/emit/adf-to-markdown.ts'
 import { adfToPlainMarkdown, reduceToPlain } from '../markdown/emit/plain-reduction.ts'
 import { directivePrefix } from '../markdown/directive-syntax.ts'
 import { markdownToAdf, plainMarkdownToAdf } from '../markdown/parse/markdown-to-adf.ts'
+import { toEditorNormal } from '../adf/editor-normal.ts'
 
 const gateRuns = 1600
 const renamedPrefix = '!adg:'
@@ -61,3 +62,12 @@ test('a generated document writes plain markdown refusing only what the guard re
     propertyRuns(gateRuns),
   )
 })
+
+test('a generated document writes the plain markdown its editor-normal form writes', { timeout: propertyTimeout }, () => {
+  fc.assert(
+    fc.property(adfDocument, (document) => {
+      assert.deepEqual(adfToPlainMarkdown(document), adfToPlainMarkdown(toEditorNormal(document)))
+    }),
+    propertyRuns(gateRuns),
+  )
+})