payments/p2wpkh: fix exception messages

src/payments/p2wpkh.js

@@ -118,9 +118,9 @@ function p2wpkh (a, opts) {
     }
 
     if (a.witness) {
-      if (a.witness.length !== 2) throw new TypeError('Input is invalid')
-      if (!bscript.isCanonicalScriptSignature(a.witness[0])) throw new TypeError('Input has invalid signature')
-      if (!ecc.isPoint(a.witness[1])) throw new TypeError('Input has invalid pubkey')
+      if (a.witness.length !== 2) throw new TypeError('Witness is invalid')
+      if (!bscript.isCanonicalScriptSignature(a.witness[0])) throw new TypeError('Witness has invalid signature')
+      if (!ecc.isPoint(a.witness[1])) throw new TypeError('Witness has invalid pubkey')
 
       if (a.signature && !a.signature.equals(a.witness[0])) throw new TypeError('Signature mismatch')
       if (a.pubkey && !a.pubkey.equals(a.witness[1])) throw new TypeError('Pubkey mismatch')

test/fixtures/p2wpkh.json

@@ -148,7 +148,13 @@
       }
     },
     {
-      "exception": "Input has invalid signature",
+      "exception": "Witness is invalid",
+      "arguments": {
+        "witness": []
+      }
+    },
+    {
+      "exception": "Witness has invalid signature",
       "arguments": {
         "witness": [
           "ffffffffffffffffff",
@@ -157,7 +163,7 @@
       }
     },
     {
-      "exception": "Input has invalid pubkey",
+      "exception": "Witness has invalid pubkey",
       "arguments": {
         "witness": [
           "300602010002010001",