tapsend: add err test case for stxo proof

This commit adds a test case for the creation of suffix proofs where the
stxo proofs are not created. This results in an specific error being
returned. The test case ensures that the expected error message is
returned.

Author: gijswijs

tapsend/proof_test.go

@@ -27,6 +27,32 @@ var (
 // TestCreateProofSuffix tests the creation of suffix proofs for a given anchor
 // transaction.
 func TestCreateProofSuffix(t *testing.T) {
+	testCases := []struct {
+		name        string
+		stxoProof   bool
+		expectedErr string
+	}{
+		{
+			name:      "Correct inclusion and exclusion proofs",
+			stxoProof: true,
+		},
+		{
+			name:      "No stxo proof",
+			stxoProof: false,
+			expectedErr: "error verifying STXO proof: missing " +
+				"asset proof",
+		},
+	}
+	for _, tc := range testCases {
+		tc := tc
+
+		t.Run(tc.name, func(tt *testing.T) {
+			createProofSuffix(t, tc.stxoProof, tc.expectedErr)
+		})
+	}
+}
+
+func createProofSuffix(t *testing.T, stxoProof bool, expectedErr string) {
 	testAssets := []*asset.Asset{
 		asset.RandAsset(t, asset.RandAssetType(t)),
 		asset.RandAsset(t, asset.RandAssetType(t)),
@@ -83,7 +109,10 @@ func TestCreateProofSuffix(t *testing.T) {
 	}
 	outputCommitments := make(map[uint32]*commitment.TapCommitment)
 
-	addOutputCommitment(t, anchorTx, outputCommitments, testPackets...)
+	addOutputCommitment(
+		t, anchorTx, outputCommitments, stxoProof,
+		testPackets...,
+	)
 	addBip86Output(t, anchorTx.FundedPsbt.Pkt)
 
 	// Create a proof suffix for all 4 packets now and validate it.
@@ -106,18 +135,34 @@ func TestCreateProofSuffix(t *testing.T) {
 			)
 
 			// Checking the transfer witness is the very last step
-			// of the proof verification. Since we didn't properly
+			// of the proof verification. Since we don't properly
 			// sign the transfer, we expect the witness to be
 			// invalid. But if we get to that point, we know that
-			// all inclusion and exclusion proofs are correct (which
-			// is what this test is testing).
+			// all inclusion and exclusion proofs are correct. So
+			// for successful cases we still expect an error, namely
+			// the invalid witness error.
+			errCode := txscript.ErrTaprootSigInvalid
 			invalidWitnessErr := vm.Error{
 				Kind: vm.ErrInvalidTransferWitness,
 				Inner: txscript.Error{
-					ErrorCode: txscript.ErrTaprootSigInvalid,
+					ErrorCode: errCode,
 				},
 			}
-			require.ErrorIs(t, err, invalidWitnessErr)
+			if expectedErr == "" {
+				require.ErrorIs(t, err, invalidWitnessErr)
+
+				continue
+			}
+
+			if vPkt.Outputs[outIdx].Asset.IsTransferRoot() {
+				require.ErrorContains(
+					t, err, expectedErr,
+				)
+			} else {
+				require.ErrorIs(
+					t, err, invalidWitnessErr,
+				)
+			}
 		}
 	}
 }
@@ -206,7 +251,7 @@ func createPacket(t *testing.T, a *asset.Asset, split bool,
 
 func addOutputCommitment(t *testing.T, anchorTx *AnchorTransaction,
 	outputCommitments map[uint32]*commitment.TapCommitment,
-	vPackets ...*tappsbt.VPacket) {
+	stxoProof bool, vPackets ...*tappsbt.VPacket) {
 
 	packet := anchorTx.FundedPsbt.Pkt
 
@@ -245,8 +290,10 @@ func addOutputCommitment(t *testing.T, anchorTx *AnchorTransaction,
 
 		c, err := commitment.FromAssets(nil, assets...)
 		require.NoError(t, err)
-		err = c.MergeAltLeaves(stxoAssetsByOutput[idx1])
-		require.NoError(t, err)
+		if stxoProof {
+			err = c.MergeAltLeaves(stxoAssetsByOutput[idx1])
+			require.NoError(t, err)
+		}
 
 		internalKey := keyByOutput[idx1]
 		script, err := tapscript.PayToAddrScript(*internalKey, nil, *c)