asset: add more test cases for ExternalKey.PubKey

Added more derivation paths and corresponding public keys, check in the test
that the values returned by the method match to expected values. Also added
tpub (testnet xpub).

To run "chantools derivekey" with xpubs, use PR
lightninglabs/chantools#179

asset/asset_test.go

@@ -1309,11 +1309,23 @@ func TestExternalKeyPubKey(t *testing.T) {
 		return *xpub
 	}
 
+	dummyXPubTestnet := func() hdkeychain.ExtendedKey {
+		xpubStr := "tpubDDfTBtwwqxXuCej7pKYfbXeCW3inAtv1cw4knmvYTTHk" +
+			"w3NoKaeCNH5XdY6n6fnBPc1gWEgeurfmBVzJLfBB1hGU64LsHFz" +
+			"Jv4ASqaHyALH"
+		xpub, err := hdkeychain.NewKeyFromString(xpubStr)
+		if err != nil {
+			panic("failed to create xpub: " + err.Error())
+		}
+		return *xpub
+	}
+
 	testCases := []struct {
-		name          string
-		externalKey   ExternalKey
-		expectError   bool
-		expectedError string
+		name           string
+		externalKey    ExternalKey
+		expectedPubKey string
+		expectError    bool
+		expectedError  string
 	}{
 		{
 			name: "valid BIP-86 external key",
@@ -1327,6 +1339,11 @@ func TestExternalKeyPubKey(t *testing.T) {
 				},
 			},
 			expectError: false,
+
+			// The pubkey was generated with "chantools derivekey
+			// --rootkey xpub... --path "m/0/0" --neuter" command.
+			expectedPubKey: "02c0ca6c5d4dc4899de975f17f1023e424a" +
+				"93a7ba6339cbaf514689f75d51787cc",
 		},
 		{
 			name: "invalid derivation path length",
@@ -1358,9 +1375,114 @@ func TestExternalKeyPubKey(t *testing.T) {
 			expectedError: "xpub must be derived from BIP-0086 " +
 				"(Taproot) derivation path",
 		},
+		{
+			name: "valid BIP-86 external key, custom coin_type",
+			externalKey: ExternalKey{
+				XPub:              dummyXPub(),
+				MasterFingerprint: 0x12345678,
+				DerivationPath: []uint32{
+					86 + hdkeychain.HardenedKeyStart,
+					42 + hdkeychain.HardenedKeyStart,
+					0 + hdkeychain.HardenedKeyStart, 0, 0,
+				},
+			},
+			expectError: false,
 
-		// TODO(ffranr): Add test(s) for positive case: valid xpub and
-		//  valid known correct corresponding public key.
+			// The pubkey was generated with "chantools derivekey
+			// --rootkey xpub... --path m/0/0 --neuter" command.
+			expectedPubKey: "02c0ca6c5d4dc4899de975f17f1023e424a" +
+				"93a7ba6339cbaf514689f75d51787cc",
+		},
+		{
+			name: "valid BIP-86 external key, custom account",
+			externalKey: ExternalKey{
+				XPub:              dummyXPub(),
+				MasterFingerprint: 0x12345678,
+				DerivationPath: []uint32{
+					86 + hdkeychain.HardenedKeyStart,
+					0 + hdkeychain.HardenedKeyStart,
+					42 + hdkeychain.HardenedKeyStart, 0, 0,
+				},
+			},
+			expectError: false,
+
+			// The pubkey was generated with "chantools derivekey
+			// --rootkey xpub... --path m/0/0 --neuter" command.
+			expectedPubKey: "02c0ca6c5d4dc4899de975f17f1023e424a" +
+				"93a7ba6339cbaf514689f75d51787cc",
+		},
+		{
+			name: "valid BIP-86 external key, change output",
+			externalKey: ExternalKey{
+				XPub:              dummyXPub(),
+				MasterFingerprint: 0x12345678,
+				DerivationPath: []uint32{
+					86 + hdkeychain.HardenedKeyStart,
+					0 + hdkeychain.HardenedKeyStart,
+					0 + hdkeychain.HardenedKeyStart, 1, 0,
+				},
+			},
+			expectError: false,
+
+			// The pubkey was generated with "chantools derivekey
+			// --rootkey xpub... --path m/1/0 --neuter" command.
+			expectedPubKey: "02ce0e73519634aaf1a34cc17afb517a697" +
+				"95c063386030f1b1b724410a84aa709",
+		},
+		{
+			name: "valid BIP-86 external key, change=2",
+			externalKey: ExternalKey{
+				XPub:              dummyXPub(),
+				MasterFingerprint: 0x12345678,
+				DerivationPath: []uint32{
+					86 + hdkeychain.HardenedKeyStart,
+					0 + hdkeychain.HardenedKeyStart,
+					0 + hdkeychain.HardenedKeyStart, 2, 0,
+				},
+			},
+			expectError: false,
+
+			// The pubkey was generated with "chantools derivekey
+			// --rootkey xpub... --path m/2/0 --neuter" command.
+			expectedPubKey: "0278b9669141d21f0598cc44a427c5d03a3" +
+				"5d6aaed5555931a99a1659dfea4ebcf",
+		},
+		{
+			name: "valid BIP-86 external key, index=2",
+			externalKey: ExternalKey{
+				XPub:              dummyXPub(),
+				MasterFingerprint: 0x12345678,
+				DerivationPath: []uint32{
+					86 + hdkeychain.HardenedKeyStart,
+					0 + hdkeychain.HardenedKeyStart,
+					0 + hdkeychain.HardenedKeyStart, 0, 2,
+				},
+			},
+			expectError: false,
+
+			// The pubkey was generated with "chantools derivekey
+			// --rootkey xpub... --path "m/0/2" --neuter" command.
+			expectedPubKey: "0375e49d472c25d1138a5526b9b7a0198e1" +
+				"d692cc3fd0133f260aca446e1244ff9",
+		},
+		{
+			name: "valid BIP-86 external key, testnet",
+			externalKey: ExternalKey{
+				XPub:              dummyXPubTestnet(),
+				MasterFingerprint: 0x12345678,
+				DerivationPath: []uint32{
+					86 + hdkeychain.HardenedKeyStart,
+					1 + hdkeychain.HardenedKeyStart,
+					0 + hdkeychain.HardenedKeyStart, 0, 0,
+				},
+			},
+			expectError: false,
+
+			// The pubkey was generated with "chantools derivekey
+			// --testnet --rootkey xpub... --path "m/0/0" --neuter".
+			expectedPubKey: "0280a3fcbeb7f770af6dd45cb0f4d02e104" +
+				"4eafe0d8b05bcaec79dc0478c7fa0da",
+		},
 	}
 
 	for _, tc := range testCases {
@@ -1375,10 +1497,16 @@ func TestExternalKeyPubKey(t *testing.T) {
 						tc.expectedError,
 					)
 				}
-			} else {
-				require.NoError(tt, err)
-				require.IsType(tt, btcec.PublicKey{}, pubKey)
+
+				return
 			}
+
+			require.NoError(tt, err)
+			require.IsType(tt, btcec.PublicKey{}, pubKey)
+			pubKeyHex := hex.EncodeToString(
+				pubKey.SerializeCompressed(),
+			)
+			require.Equal(tt, tc.expectedPubKey, pubKeyHex)
 		})
 	}
 }