Add HMAC length tests

src/test/java/com/eatthepath/noise/crypto/AbstractBlake2HmacTest.java

@@ -0,0 +1,27 @@
+package com.eatthepath.noise.crypto;
+
+import org.junit.jupiter.api.Test;
+
+import javax.crypto.Mac;
+import javax.crypto.spec.SecretKeySpec;
+
+import java.security.InvalidKeyException;
+import java.security.Key;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+abstract class AbstractBlake2HmacTest {
+
+  protected abstract Mac getHmac();
+
+  @Test
+  void getMacLength() throws InvalidKeyException {
+    final Key key = new SecretKeySpec(new byte[32], "RAW");
+
+    final Mac hmac = getHmac();
+    hmac.init(key);
+    hmac.update(new byte[32]);
+
+    assertEquals(hmac.getMacLength(), hmac.doFinal().length);
+  }
+}

src/test/java/com/eatthepath/noise/crypto/HmacBlake2b512MacTest.java

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+package com.eatthepath.noise.crypto;
+
+import javax.crypto.Mac;
+
+class HmacBlake2b512MacTest extends AbstractBlake2HmacTest {
+
+  @Override
+  protected Mac getHmac() {
+    return new HmacBlake2b512Mac();
+  }
+}

src/test/java/com/eatthepath/noise/crypto/HmacBlake2s256MacTest.java

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+package com.eatthepath.noise.crypto;
+
+import javax.crypto.Mac;
+
+class HmacBlake2s256MacTest extends AbstractBlake2HmacTest {
+
+  @Override
+  protected Mac getHmac() {
+    return new HmacBlake2s256Mac();
+  }
+}