test: complete coverage of querystring

PR-URL: #38520
Refs: https://coverage.nodejs.org/coverage-68e6673224365120/lib/querystring.js.html#L179
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Zijian Liu <lxxyxzj@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>

test/parallel/test-querystring.js

@@ -307,6 +307,7 @@ assert.strictEqual(qs.stringify({ foo: -0 }), 'foo=0');
 assert.strictEqual(qs.stringify({ foo: 3 }), 'foo=3');
 assert.strictEqual(qs.stringify({ foo: -72.42 }), 'foo=-72.42');
 assert.strictEqual(qs.stringify({ foo: NaN }), 'foo=');
+assert.strictEqual(qs.stringify({ foo: 1e21 }), 'foo=1e%2B21');
 assert.strictEqual(qs.stringify({ foo: Infinity }), 'foo=');
 
 // nested
@@ -450,6 +451,14 @@ check(qs.parse('%\u0100=%\u0101'), { '%Ā': '%ā' });
     'a=a&b=b&c=c');
 }
 
+// Test custom encode for different types
+{
+  const obj = { number: 1, bigint: 2n, true: true, false: false, object: {} };
+  assert.strictEqual(
+    qs.stringify(obj, null, null, { encodeURIComponent: (v) => v }),
+    'number=1&bigint=2&true=true&false=false&object=');
+}
+
 // Test QueryString.unescapeBuffer
 qsUnescapeTestCases.forEach((testCase) => {
   assert.strictEqual(qs.unescape(testCase[0]), testCase[1]);