buffer, test: add tests for buffer.toJSON

* Pull out the tests for buffer.toJSON from test-buffer-alloc
* Add tests for serializing a 0-length buffer

PR-URL: nodejs/node#10979
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-buffer-alloc.js

@@ -769,30 +769,6 @@ assert.strictEqual(Buffer.from('13.37').length, 5);
 // issue GH-3416
 Buffer.from(Buffer.allocUnsafe(0), 0, 0);
 
-// GH-5110
-{
-  const buffer = Buffer.from('test');
-  const string = JSON.stringify(buffer);
-
-  assert.strictEqual(string, '{"type":"Buffer","data":[116,101,115,116]}');
-
-  assert.deepStrictEqual(buffer, JSON.parse(string, (key, value) => {
-    return value && value.type === 'Buffer' ?
-      Buffer.from(value.data) :
-      value;
-  }));
-}
-
-// issue GH-7849
-{
-  const buf = Buffer.from('test');
-  const json = JSON.stringify(buf);
-  const obj = JSON.parse(json);
-  const copy = Buffer.from(obj);
-
-  assert(buf.equals(copy));
-}
-
 // issue GH-5587
 assert.throws(() => Buffer.alloc(8).writeFloatLE(0, 5), RangeError);
 assert.throws(() => Buffer.alloc(16).writeDoubleLE(0, 9), RangeError);

test/parallel/test-buffer-tojson.js

@@ -0,0 +1,36 @@
+'use strict';
+
+require('../common');
+const assert = require('assert');
+const Buffer = require('buffer').Buffer;
+
+{
+  assert.strictEqual(JSON.stringify(Buffer.alloc(0)),
+                     '{"type":"Buffer","data":[]}');
+  assert.strictEqual(JSON.stringify(Buffer.from([1, 2, 3, 4])),
+                     '{"type":"Buffer","data":[1,2,3,4]}');
+}
+
+// issue GH-7849
+{
+  const buf = Buffer.from('test');
+  const json = JSON.stringify(buf);
+  const obj = JSON.parse(json);
+  const copy = Buffer.from(obj);
+
+  assert.deepStrictEqual(buf, copy);
+}
+
+// GH-5110
+{
+  const buffer = Buffer.from('test');
+  const string = JSON.stringify(buffer);
+
+  assert.strictEqual(string, '{"type":"Buffer","data":[116,101,115,116]}');
+
+  function receiver(key, value) {
+    return value && value.type === 'Buffer' ? Buffer.from(value.data) : value;
+  }
+
+  assert.deepStrictEqual(buffer, JSON.parse(string, receiver));
+}