Implement HMAC support in lib/crypto.

tests/lib/src/crypto/sha1_test.dart

Index: tests/lib/src/crypto/sha1_test.dart
diff --git a/tests/lib/src/crypto/sha1Test.dart b/tests/lib/src/crypto/sha1_test.dart
similarity index 99%
rename from tests/lib/src/crypto/sha1Test.dart
rename to tests/lib/src/crypto/sha1_test.dart
index 88334eb10b54b3ba331874ff7b7151159cf1f42d..4153e596d9b9ce4abcecaaf4c89d3211c03211c0 100644
--- a/tests/lib/src/crypto/sha1Test.dart
+++ b/tests/lib/src/crypto/sha1_test.dart
@@ -548,10 +548,13 @@ void test() {
 void testInvalidUse() {
   var sha = new SHA1();
   sha.digest();
-  Expect.throws(sha.digest,
-                (e) => e is CryptoHashException);
-  Expect.throws(() => sha.update([0]),
-                (e) => e is CryptoHashException);
+  Expect.throws(() => sha.update([0]), (e) => e is HashException);
+}
+
+void testRepeatedDigest() {
+  var sha = new SHA1();
+  var digest = sha.digest();
+  Expect.listEquals(digest, sha.digest());
 }
 
 void testStandardVectors(inputs, mds) {
@@ -564,6 +567,7 @@ void testStandardVectors(inputs, mds) {
 void main() {
   test();
   testInvalidUse();
+  testRepeatedDigest();
   testStandardVectors(sha1_long_inputs, sha1_long_mds);
   testStandardVectors(sha1_short_inputs, sha1_short_mds);
 }