revert encoding 'fix' and add unit test.

veilid-flutter/test/test_encoding.dart

@@ -0,0 +1,70 @@
+import 'dart:convert';
+import 'dart:math';
+import 'dart:typed_data';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:veilid/veilid_encoding.dart';
+
+const knownVectors = [
+  ['', ''],
+  ['f', 'Zg'],
+  ['fo', 'Zm8'],
+  ['foo', 'Zm9v'],
+  ['foob', 'Zm9vYg'],
+  ['fooba', 'Zm9vYmE'],
+  ['foobar', 'Zm9vYmFy']
+];
+
+Future<void> _testEncodingKnownVector(Uint8List k, String v) async {
+  final e = base64UrlNoPadEncode(k);
+  expect(e, v, reason: 'encode mismatch');
+
+  final d = base64UrlNoPadDecode(v);
+  expect(d, k, reason: 'decode mismatch');
+
+  final r = base64UrlNoPadDecode(e);
+  expect(r, k, reason: 'round trip mismatch');
+}
+
+Future<void> testEncodingKnownVectors() async {
+  for (final kv in knownVectors) {
+    final k = Uint8List.fromList(kv[0].codeUnits);
+    final v = kv[1];
+
+    await _testEncodingKnownVector(k, v);
+  }
+}
+
+Future<void> testEncodeDecodeGarbage() async {
+  final random = Random(0);
+  for (var n = 0; n < 8192; n++) {
+    final kl = List<int>.empty(growable: true);
+    for (var p = 0; p < n; p++) {
+      final v = random.nextInt(256);
+      kl.add(v);
+    }
+    final k = Uint8List.fromList(kl);
+
+    final e = base64UrlNoPadEncode(k);
+    final r = base64UrlNoPadDecode(e);
+
+    expect(r, k, reason: 'garbage round trip mismatch');
+  }
+}
+
+Future<void> testEncodeDecodeGarbagePad() async {
+  final random = Random(0);
+  for (var n = 0; n < 8192; n++) {
+    final kl = List<int>.empty(growable: true);
+    for (var p = 0; p < n; p++) {
+      final v = random.nextInt(256);
+      kl.add(v);
+    }
+    final k = Uint8List.fromList(kl);
+
+    final e = base64Url.encode(k);
+    final r = base64UrlNoPadDecode(e);
+
+    expect(r, k, reason: 'garbage w/pad round trip mismatch');
+  }
+}