test: test hmac binding robustness

The Hmac binding layer is not documented as part of the API, and is not
intended to be used, but it should be robust to misuse, and contains
defensive checks for misuse. This test checks that updates without init
throw (as opposed to abort or misbehave in some other way).

PR-URL: nodejs#10923
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-crypto-hmac.js

@@ -8,6 +8,14 @@ if (!common.hasCrypto) {
 }
 var crypto = require('crypto');
 
+// Test for binding layer robustness
+{
+  const binding = process.binding('crypto');
+  const h = new binding.Hmac();
+  // Fail to init the Hmac with an algorithm.
+  assert.throws(() => h.update('hello'), /^TypeError: HmacUpdate fail$/);
+}
+
 // Test HMAC
 var h1 = crypto.createHmac('sha1', 'Node')
                .update('some data')