diff --git a/test/parallel/test-buffer-alloc.js b/test/parallel/test-buffer-alloc.js
index 597b925be20f43..1368136abe8f22 100644
--- a/test/parallel/test-buffer-alloc.js
+++ b/test/parallel/test-buffer-alloc.js
@@ -314,6 +314,8 @@ assert.strictEqual((Buffer.from('Woman')).toString('base64url'), 'V29tYW4');
                          Buffer.from(expected));
 }
 
+const base64flavors = ['base64', 'base64url'];
+
 {
   // Test that regular and URL-safe base64 both work both ways with padding
   const expected = [0xff, 0xff, 0xbe, 0xff, 0xef, 0xbf, 0xfb, 0xef, 0xff, 0xfb];
@@ -341,137 +343,182 @@ assert.strictEqual((Buffer.from('Woman')).toString('base64url'), 'V29tYW4');
                    'dWVkIGFuZCBpbmRlZmF0aWdhYmxlIGdlbmVyYXRpb24gb2Yga25vd2xlZ' +
                    'GdlLCBleGNlZWRzIHRoZSBzaG9ydCB2ZWhlbWVuY2Ugb2YgYW55IGNhcm' +
                    '5hbCBwbGVhc3VyZS4=';
-  assert.strictEqual((Buffer.from(quote)).toString('base64'), expected);
-
-  let b = Buffer.allocUnsafe(1024);
-  let bytesWritten = b.write(expected, 0, 'base64');
-  assert.strictEqual(quote.length, bytesWritten);
-  assert.strictEqual(quote, b.toString('ascii', 0, quote.length));
-
-  // Check that the base64 decoder ignores whitespace
-  const expectedWhite = `${expected.slice(0, 60)} \n` +
-                        `${expected.slice(60, 120)} \n` +
-                        `${expected.slice(120, 180)} \n` +
-                        `${expected.slice(180, 240)} \n` +
-                        `${expected.slice(240, 300)}\n` +
-                        `${expected.slice(300, 360)}\n`;
-  b = Buffer.allocUnsafe(1024);
-  bytesWritten = b.write(expectedWhite, 0, 'base64');
-  assert.strictEqual(quote.length, bytesWritten);
-  assert.strictEqual(quote, b.toString('ascii', 0, quote.length));
-
-  // Check that the base64 decoder on the constructor works
-  // even in the presence of whitespace.
-  b = Buffer.from(expectedWhite, 'base64');
-  assert.strictEqual(quote.length, b.length);
-  assert.strictEqual(quote, b.toString('ascii', 0, quote.length));
-
-  // Check that the base64 decoder ignores illegal chars
-  const expectedIllegal = expected.slice(0, 60) + ' \x80' +
-                          expected.slice(60, 120) + ' \xff' +
-                          expected.slice(120, 180) + ' \x00' +
-                          expected.slice(180, 240) + ' \x98' +
-                          expected.slice(240, 300) + '\x03' +
-                          expected.slice(300, 360);
-  b = Buffer.from(expectedIllegal, 'base64');
-  assert.strictEqual(quote.length, b.length);
-  assert.strictEqual(quote, b.toString('ascii', 0, quote.length));
+  assert.strictEqual(Buffer.from(quote).toString('base64'), expected);
+  assert.strictEqual(
+    Buffer.from(quote).toString('base64url'),
+    expected.replaceAll('+', '-').replaceAll('/', '_').replaceAll('=', '')
+  );
+
+  base64flavors.forEach((encoding) => {
+    let b = Buffer.allocUnsafe(1024);
+    let bytesWritten = b.write(expected, 0, encoding);
+    assert.strictEqual(quote.length, bytesWritten);
+    assert.strictEqual(quote, b.toString('ascii', 0, quote.length));
+
+    // Check that the base64 decoder ignores whitespace
+    const expectedWhite = `${expected.slice(0, 60)} \n` +
+                          `${expected.slice(60, 120)} \n` +
+                          `${expected.slice(120, 180)} \n` +
+                          `${expected.slice(180, 240)} \n` +
+                          `${expected.slice(240, 300)}\n` +
+                          `${expected.slice(300, 360)}\n`;
+    b = Buffer.allocUnsafe(1024);
+    bytesWritten = b.write(expectedWhite, 0, encoding);
+    assert.strictEqual(quote.length, bytesWritten);
+    assert.strictEqual(quote, b.toString('ascii', 0, quote.length));
+
+    // Check that the base64 decoder on the constructor works
+    // even in the presence of whitespace.
+    b = Buffer.from(expectedWhite, encoding);
+    assert.strictEqual(quote.length, b.length);
+    assert.strictEqual(quote, b.toString('ascii', 0, quote.length));
+
+    // Check that the base64 decoder ignores illegal chars
+    const expectedIllegal = expected.slice(0, 60) + ' \x80' +
+                            expected.slice(60, 120) + ' \xff' +
+                            expected.slice(120, 180) + ' \x00' +
+                            expected.slice(180, 240) + ' \x98' +
+                            expected.slice(240, 300) + '\x03' +
+                            expected.slice(300, 360);
+    b = Buffer.from(expectedIllegal, encoding);
+    assert.strictEqual(quote.length, b.length);
+    assert.strictEqual(quote, b.toString('ascii', 0, quote.length));
+  });
 }
 
-assert.strictEqual(Buffer.from('', 'base64').toString(), '');
-assert.strictEqual(Buffer.from('K', 'base64').toString(), '');
-
-// multiple-of-4 with padding
-assert.strictEqual(Buffer.from('Kg==', 'base64').toString(), '*');
-assert.strictEqual(Buffer.from('Kio=', 'base64').toString(), '*'.repeat(2));
-assert.strictEqual(Buffer.from('Kioq', 'base64').toString(), '*'.repeat(3));
-assert.strictEqual(Buffer.from('KioqKg==', 'base64').toString(), '*'.repeat(4));
-assert.strictEqual(Buffer.from('KioqKio=', 'base64').toString(), '*'.repeat(5));
-assert.strictEqual(Buffer.from('KioqKioq', 'base64').toString(), '*'.repeat(6));
-assert.strictEqual(Buffer.from('KioqKioqKg==', 'base64').toString(),
-                   '*'.repeat(7));
-assert.strictEqual(Buffer.from('KioqKioqKio=', 'base64').toString(),
-                   '*'.repeat(8));
-assert.strictEqual(Buffer.from('KioqKioqKioq', 'base64').toString(),
-                   '*'.repeat(9));
-assert.strictEqual(Buffer.from('KioqKioqKioqKg==', 'base64').toString(),
-                   '*'.repeat(10));
-assert.strictEqual(Buffer.from('KioqKioqKioqKio=', 'base64').toString(),
-                   '*'.repeat(11));
-assert.strictEqual(Buffer.from('KioqKioqKioqKioq', 'base64').toString(),
-                   '*'.repeat(12));
-assert.strictEqual(Buffer.from('KioqKioqKioqKioqKg==', 'base64').toString(),
-                   '*'.repeat(13));
-assert.strictEqual(Buffer.from('KioqKioqKioqKioqKio=', 'base64').toString(),
-                   '*'.repeat(14));
-assert.strictEqual(Buffer.from('KioqKioqKioqKioqKioq', 'base64').toString(),
-                   '*'.repeat(15));
-assert.strictEqual(Buffer.from('KioqKioqKioqKioqKioqKg==', 'base64').toString(),
-                   '*'.repeat(16));
-assert.strictEqual(Buffer.from('KioqKioqKioqKioqKioqKio=', 'base64').toString(),
-                   '*'.repeat(17));
-assert.strictEqual(Buffer.from('KioqKioqKioqKioqKioqKioq', 'base64').toString(),
-                   '*'.repeat(18));
-assert.strictEqual(Buffer.from('KioqKioqKioqKioqKioqKioqKg==',
-                               'base64').toString(),
-                   '*'.repeat(19));
-assert.strictEqual(Buffer.from('KioqKioqKioqKioqKioqKioqKio=',
-                               'base64').toString(),
-                   '*'.repeat(20));
-
-// No padding, not a multiple of 4
-assert.strictEqual(Buffer.from('Kg', 'base64').toString(), '*');
-assert.strictEqual(Buffer.from('Kio', 'base64').toString(), '*'.repeat(2));
-assert.strictEqual(Buffer.from('KioqKg', 'base64').toString(), '*'.repeat(4));
-assert.strictEqual(Buffer.from('KioqKio', 'base64').toString(), '*'.repeat(5));
-assert.strictEqual(Buffer.from('KioqKioqKg', 'base64').toString(),
-                   '*'.repeat(7));
-assert.strictEqual(Buffer.from('KioqKioqKio', 'base64').toString(),
-                   '*'.repeat(8));
-assert.strictEqual(Buffer.from('KioqKioqKioqKg', 'base64').toString(),
-                   '*'.repeat(10));
-assert.strictEqual(Buffer.from('KioqKioqKioqKio', 'base64').toString(),
-                   '*'.repeat(11));
-assert.strictEqual(Buffer.from('KioqKioqKioqKioqKg', 'base64').toString(),
-                   '*'.repeat(13));
-assert.strictEqual(Buffer.from('KioqKioqKioqKioqKio', 'base64').toString(),
-                   '*'.repeat(14));
-assert.strictEqual(Buffer.from('KioqKioqKioqKioqKioqKg', 'base64').toString(),
-                   '*'.repeat(16));
-assert.strictEqual(Buffer.from('KioqKioqKioqKioqKioqKio', 'base64').toString(),
-                   '*'.repeat(17));
-assert.strictEqual(Buffer.from('KioqKioqKioqKioqKioqKioqKg',
-                               'base64').toString(),
-                   '*'.repeat(19));
-assert.strictEqual(Buffer.from('KioqKioqKioqKioqKioqKioqKio',
-                               'base64').toString(),
-                   '*'.repeat(20));
+base64flavors.forEach((encoding) => {
+  assert.strictEqual(Buffer.from('', encoding).toString(), '');
+  assert.strictEqual(Buffer.from('K', encoding).toString(), '');
+
+  // multiple-of-4 with padding
+  assert.strictEqual(Buffer.from('Kg==', encoding).toString(), '*');
+  assert.strictEqual(Buffer.from('Kio=', encoding).toString(), '*'.repeat(2));
+  assert.strictEqual(Buffer.from('Kioq', encoding).toString(), '*'.repeat(3));
+  assert.strictEqual(
+    Buffer.from('KioqKg==', encoding).toString(), '*'.repeat(4));
+  assert.strictEqual(
+    Buffer.from('KioqKio=', encoding).toString(), '*'.repeat(5));
+  assert.strictEqual(
+    Buffer.from('KioqKioq', encoding).toString(), '*'.repeat(6));
+  assert.strictEqual(Buffer.from('KioqKioqKg==', encoding).toString(),
+                     '*'.repeat(7));
+  assert.strictEqual(Buffer.from('KioqKioqKio=', encoding).toString(),
+                     '*'.repeat(8));
+  assert.strictEqual(Buffer.from('KioqKioqKioq', encoding).toString(),
+                     '*'.repeat(9));
+  assert.strictEqual(Buffer.from('KioqKioqKioqKg==', encoding).toString(),
+                     '*'.repeat(10));
+  assert.strictEqual(Buffer.from('KioqKioqKioqKio=', encoding).toString(),
+                     '*'.repeat(11));
+  assert.strictEqual(Buffer.from('KioqKioqKioqKioq', encoding).toString(),
+                     '*'.repeat(12));
+  assert.strictEqual(Buffer.from('KioqKioqKioqKioqKg==', encoding).toString(),
+                     '*'.repeat(13));
+  assert.strictEqual(Buffer.from('KioqKioqKioqKioqKio=', encoding).toString(),
+                     '*'.repeat(14));
+  assert.strictEqual(Buffer.from('KioqKioqKioqKioqKioq', encoding).toString(),
+                     '*'.repeat(15));
+  assert.strictEqual(
+    Buffer.from('KioqKioqKioqKioqKioqKg==', encoding).toString(),
+    '*'.repeat(16));
+  assert.strictEqual(
+    Buffer.from('KioqKioqKioqKioqKioqKio=', encoding).toString(),
+    '*'.repeat(17));
+  assert.strictEqual(
+    Buffer.from('KioqKioqKioqKioqKioqKioq', encoding).toString(),
+    '*'.repeat(18));
+  assert.strictEqual(Buffer.from('KioqKioqKioqKioqKioqKioqKg==',
+                                 encoding).toString(),
+                     '*'.repeat(19));
+  assert.strictEqual(Buffer.from('KioqKioqKioqKioqKioqKioqKio=',
+                                 encoding).toString(),
+                     '*'.repeat(20));
+
+  // No padding, not a multiple of 4
+  assert.strictEqual(Buffer.from('Kg', encoding).toString(), '*');
+  assert.strictEqual(Buffer.from('Kio', encoding).toString(), '*'.repeat(2));
+  assert.strictEqual(Buffer.from('KioqKg', encoding).toString(), '*'.repeat(4));
+  assert.strictEqual(
+    Buffer.from('KioqKio', encoding).toString(), '*'.repeat(5));
+  assert.strictEqual(Buffer.from('KioqKioqKg', encoding).toString(),
+                     '*'.repeat(7));
+  assert.strictEqual(Buffer.from('KioqKioqKio', encoding).toString(),
+                     '*'.repeat(8));
+  assert.strictEqual(Buffer.from('KioqKioqKioqKg', encoding).toString(),
+                     '*'.repeat(10));
+  assert.strictEqual(Buffer.from('KioqKioqKioqKio', encoding).toString(),
+                     '*'.repeat(11));
+  assert.strictEqual(Buffer.from('KioqKioqKioqKioqKg', encoding).toString(),
+                     '*'.repeat(13));
+  assert.strictEqual(Buffer.from('KioqKioqKioqKioqKio', encoding).toString(),
+                     '*'.repeat(14));
+  assert.strictEqual(Buffer.from('KioqKioqKioqKioqKioqKg', encoding).toString(),
+                     '*'.repeat(16));
+  assert.strictEqual(
+    Buffer.from('KioqKioqKioqKioqKioqKio', encoding).toString(),
+    '*'.repeat(17));
+  assert.strictEqual(
+    Buffer.from('KioqKioqKioqKioqKioqKioqKg', encoding).toString(),
+    '*'.repeat(19));
+  assert.strictEqual(
+    Buffer.from('KioqKioqKioqKioqKioqKioqKio', encoding).toString(),
+    '*'.repeat(20));
+});
 
 // Handle padding graciously, multiple-of-4 or not
 assert.strictEqual(
   Buffer.from('72INjkR5fchcxk9+VgdGPFJDxUBFR5/rMFsghgxADiw==', 'base64').length,
   32
 );
+assert.strictEqual(
+  Buffer.from('72INjkR5fchcxk9-VgdGPFJDxUBFR5_rMFsghgxADiw==', 'base64url')
+    .length,
+  32
+);
 assert.strictEqual(
   Buffer.from('72INjkR5fchcxk9+VgdGPFJDxUBFR5/rMFsghgxADiw=', 'base64').length,
   32
 );
+assert.strictEqual(
+  Buffer.from('72INjkR5fchcxk9-VgdGPFJDxUBFR5_rMFsghgxADiw=', 'base64url')
+    .length,
+  32
+);
 assert.strictEqual(
   Buffer.from('72INjkR5fchcxk9+VgdGPFJDxUBFR5/rMFsghgxADiw', 'base64').length,
   32
 );
+assert.strictEqual(
+  Buffer.from('72INjkR5fchcxk9-VgdGPFJDxUBFR5_rMFsghgxADiw', 'base64url')
+    .length,
+  32
+);
 assert.strictEqual(
   Buffer.from('w69jACy6BgZmaFvv96HG6MYksWytuZu3T1FvGnulPg==', 'base64').length,
   31
 );
+assert.strictEqual(
+  Buffer.from('w69jACy6BgZmaFvv96HG6MYksWytuZu3T1FvGnulPg==', 'base64url')
+    .length,
+  31
+);
 assert.strictEqual(
   Buffer.from('w69jACy6BgZmaFvv96HG6MYksWytuZu3T1FvGnulPg=', 'base64').length,
   31
 );
+assert.strictEqual(
+  Buffer.from('w69jACy6BgZmaFvv96HG6MYksWytuZu3T1FvGnulPg=', 'base64url')
+    .length,
+  31
+);
 assert.strictEqual(
   Buffer.from('w69jACy6BgZmaFvv96HG6MYksWytuZu3T1FvGnulPg', 'base64').length,
   31
 );
+assert.strictEqual(
+  Buffer.from('w69jACy6BgZmaFvv96HG6MYksWytuZu3T1FvGnulPg', 'base64url').length,
+  31
+);
 
 {
 // This string encodes single '.' character in UTF-16
@@ -483,6 +530,16 @@ assert.strictEqual(
   assert.strictEqual(dot.toString('base64'), '//4uAA==');
 }
 
+{
+// This string encodes single '.' character in UTF-16
+  const dot = Buffer.from('//4uAA', 'base64url');
+  assert.strictEqual(dot[0], 0xff);
+  assert.strictEqual(dot[1], 0xfe);
+  assert.strictEqual(dot[2], 0x2e);
+  assert.strictEqual(dot[3], 0x00);
+  assert.strictEqual(dot.toString('base64url'), '__4uAA');
+}
+
 {
   // Writing base64 at a position > 0 should not mangle the result.
   //
@@ -498,6 +555,21 @@ assert.strictEqual(
                      'Madness?! This is node.js!');
 }
 
+{
+  // Writing base64url at a position > 0 should not mangle the result.
+  //
+  // https://github.com/joyent/node/issues/402
+  const segments = ['TWFkbmVzcz8h', 'IFRoaXM', 'IGlz', 'IG5vZGUuanMh'];
+  const b = Buffer.allocUnsafe(64);
+  let pos = 0;
+
+  for (let i = 0; i < segments.length; ++i) {
+    pos += b.write(segments[i], pos, 'base64url');
+  }
+  assert.strictEqual(b.toString('latin1', 0, pos),
+                     'Madness?! This is node.js!');
+}
+
 // Regression test for https://github.com/nodejs/node/issues/3496.
 assert.strictEqual(Buffer.from('=bad'.repeat(1e4), 'base64').length, 0);