test large inputs for sha1 and sha256, also remove unused import

test/very_long_input.dart

Index: test/very_long_input.dart
diff --git a/test/very_long_input.dart b/test/very_long_input.dart
new file mode 100644
index 0000000000000000000000000000000000000000..b3e72b3e00f1761b2ce686bfde60f466bcb47c4d
--- /dev/null
+++ b/test/very_long_input.dart
@@ -0,0 +1,14 @@
+library very_long_input_test;
+
+import 'package:crypto/crypto.dart';
+import 'package:test/test.dart';
+
+veryLongInput(digester, int byteLength, String verify) {
+  var nullCharacter = '\u0000'.codeUnitAt(0);
+  var input = [nullCharacter];
+  for (var i = 0; i < byteLength; i++) {
+    digester.add(input);
+  }
+  var d = digester.close();
+  expect(CryptoUtils.bytesToHex(d), verify);
+}