test: add unit test for JSON typeCast wrapper

test/unit/parsers/test-text-parser.js

@@ -0,0 +1,38 @@
+'use strict';
+
+const assert = require('assert');
+const common = require('../../common');
+
+const typeCastWrapper = function (...args) {
+  return function (field, next) {
+    if (field.type === 'JSON') {
+      return JSON.parse(field.string(...args));
+    }
+
+    return next();
+  }
+}
+
+const connection = common.createConnection();
+connection.query('CREATE TEMPORARY TABLE t (i JSON)');
+connection.query('INSERT INTO t values(\'{ "test": "😀" }\')');
+
+// JSON without encoding options - should result in unexpected behaviors
+connection.query({
+  sql: 'SELECT * FROM t',
+  typeCast: typeCastWrapper()
+}, (err, rows) => {
+  assert.ifError(err);
+  assert.notEqual(rows[0].i.test, "😀");
+});
+
+// JSON with encoding explicitly set to utf8
+connection.query({
+  sql: 'SELECT * FROM t',
+  typeCast: typeCastWrapper("utf8")
+}, (err, rows) => {
+  assert.ifError(err);
+  assert.equal(rows[0].i.test, "😀");
+});
+
+connection.end();