zpay32: make expiry time only accessable using Expiry()

This commit renames the invoice field Expiry to expiry, and changes
the type from time.Time to time.Duration. Getting the value of the
field will now have to be done using the getter Expiry(), which
will also return the default invoice expiry (3600s) if it is not set
explicitly by the the invoice.

zpay32/invoice.go

@@ -109,9 +109,13 @@ type Invoice struct {
 	// Optional. Non-nil iff Description is nil.
 	DescriptionHash *[32]byte
 
-	// Expiry specifies the timespan this invoice will be valid.
+	// expiry specifies the timespan this invoice will be valid.
 	// Optional. If not set, a default expiry of 60 min will be implied.
-	Expiry *time.Time
+	//
+	// This field is unexported and can be read by the Expiry() method. This
+	// method makes sure the default expiry time is returned in case the
+	// field is not set.
+	expiry *time.Duration
 
 	// FallbackAddr is an on-chain address that can be used for payment in
 	// case the Lightning payment fails.
@@ -177,9 +181,9 @@ func DescriptionHash(descriptionHash [32]byte) func(*Invoice) {
 // Expiry is a functional option that allows callers of NewInvoice to set the
 // expiry of the created Invoice. If not set, a default expiry of 60 min will
 // be implied.
-func Expiry(expiry time.Time) func(*Invoice) {
+func Expiry(expiry time.Duration) func(*Invoice) {
 	return func(i *Invoice) {
-		i.Expiry = &expiry
+		i.expiry = &expiry
 	}
 }
 
@@ -444,6 +448,17 @@ func (invoice *Invoice) Encode(signer MessageSigner) (string, error) {
 	return b32, nil
 }
 
+// Expiry returns the expiry time for this invoice. If expiry time is not set
+// explicitly, the default 3600 second expiry will be returned.
+func (invoice *Invoice) Expiry() time.Duration {
+	if invoice.expiry != nil {
+		return *invoice.expiry
+	}
+
+	// If no expiry is set for this invoice, default is 3600 seconds.
+	return 3600 * time.Second
+}
+
 // validateInvoice does a sanity check of the provided Invoice, making sure it
 // has all the necessary fields set for it to be considered valid by BOLT-0011.
 func validateInvoice(invoice *Invoice) error {
@@ -624,7 +639,7 @@ func parseTaggedFields(invoice *Invoice, fields []byte, net *chaincfg.Params) er
 			copy(dHash[:], hash[:])
 			invoice.DescriptionHash = &dHash
 		case fieldTypeX:
-			if invoice.Expiry != nil {
+			if invoice.expiry != nil {
 				// We skip the field if we have already seen a
 				// supported one.
 				continue
@@ -634,8 +649,8 @@ func parseTaggedFields(invoice *Invoice, fields []byte, net *chaincfg.Params) er
 			if err != nil {
 				return err
 			}
-			unix := time.Unix(int64(exp), 0)
+			dur := time.Duration(exp) * time.Second
-			invoice.Expiry = &unix
+			invoice.expiry = &dur
 		case fieldTypeF:
 			if invoice.FallbackAddr != nil {
 				// We skip the field if we have already seen a
@@ -783,9 +798,9 @@ func writeTaggedFields(bufferBase32 *bytes.Buffer, invoice *Invoice) error {
 		}
 	}
 
-	if invoice.Expiry != nil {
+	if invoice.expiry != nil {
-		unix := invoice.Expiry.Unix()
+		seconds := invoice.expiry.Seconds()
-		expiry := uint64ToBase32(uint64(unix))
+		expiry := uint64ToBase32(uint64(seconds))
 		err := writeTaggedField(bufferBase32, fieldTypeX, expiry)
 		if err != nil {
 			return err

zpay32/invoice_test.go

@@ -29,7 +29,7 @@ var (
 	testMillisat2500uBTC = lnwire.MilliSatoshi(250000000)
 	testMillisat20mBTC   = lnwire.MilliSatoshi(2000000000)
 
-	testExpiry60             = time.Unix(60, 0)
+	testExpiry60             = 60 * time.Second
 	testEmptyString          = ""
 	testCupOfCoffee          = "1 cup coffee"
 	testPleaseConsider       = "Please consider supporting this project"
@@ -72,7 +72,7 @@ func TestDecodeEncode(t *testing.T) {
 	tests := []struct {
 		encodedInvoice string
 		valid          bool
-		decodedInvoice *zpay32.Invoice
+		decodedInvoice func() *zpay32.Invoice
 		skipEncoding   bool
 		beforeEncoding func(*zpay32.Invoice)
 	}{
@@ -112,19 +112,22 @@ func TestDecodeEncode(t *testing.T) {
 			// no payment hash set
 			encodedInvoice: "lnbc20m1pvjluezhp58yjmdan79s6qqdhdzgynm4zwqd5d7xmw5fk98klysy043l2ahrqsjv38luh6p6s2xrv3mzvlmzaya43376h0twal5ax0k6p47498hp3hnaymzhsn424rxqjs0q7apn26yrhaxltq3vzwpqj9nc2r3kzwccsplnq470",
 			valid:          false,
-			decodedInvoice: &zpay32.Invoice{
+			decodedInvoice: func() *zpay32.Invoice {
+				return &zpay32.Invoice{
 					Net:             &chaincfg.MainNetParams,
 					MilliSat:        &testMillisat20mBTC,
 					Timestamp:       time.Unix(1496314658, 0),
 					DescriptionHash: &testDescriptionHash,
 					Destination:     testPubKey,
+				}
 			},
 		},
 		{
 			// Both Description and DescriptionHash set.
 			encodedInvoice: "lnbc20m1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqdpl2pkx2ctnv5sxxmmwwd5kgetjypeh2ursdae8g6twvus8g6rfwvs8qun0dfjkxaqhp58yjmdan79s6qqdhdzgynm4zwqd5d7xmw5fk98klysy043l2ahrqs03vghs8y0kuj4ulrzls8ln7fnm9dk7sjsnqmghql6hd6jut36clkqpyuq0s5m6fhureyz0szx2qjc8hkgf4xc2hpw8jpu26jfeyvf4cpga36gt",
 			valid:          false,
-			decodedInvoice: &zpay32.Invoice{
+			decodedInvoice: func() *zpay32.Invoice {
+				return &zpay32.Invoice{
 					Net:             &chaincfg.MainNetParams,
 					MilliSat:        &testMillisat20mBTC,
 					Timestamp:       time.Unix(1496314658, 0),
@@ -132,31 +135,36 @@ func TestDecodeEncode(t *testing.T) {
 					Description:     &testPleaseConsider,
 					DescriptionHash: &testDescriptionHash,
 					Destination:     testPubKey,
+				}
 			},
 		},
 		{
 			// Neither Description nor DescriptionHash set.
 			encodedInvoice: "lnbc20m1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqn2rne0kagfl4e0xag0w6hqeg2dwgc54hrm9m0auw52dhwhwcu559qav309h598pyzn69wh2nqauneyyesnpmaax0g6acr8lh9559jmcquyq5a9",
 			valid:          false,
-			decodedInvoice: &zpay32.Invoice{
+			decodedInvoice: func() *zpay32.Invoice {
+				return &zpay32.Invoice{
 					Net:         &chaincfg.MainNetParams,
 					MilliSat:    &testMillisat20mBTC,
 					Timestamp:   time.Unix(1496314658, 0),
 					PaymentHash: &testPaymentHash,
 					Destination: testPubKey,
+				}
 			},
 		},
 		{
 			// Has a few unknown fields, should just be ignored.
 			encodedInvoice: "lnbc20m1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqdpl2pkx2ctnv5sxxmmwwd5kgetjypeh2ursdae8g6twvus8g6rfwvs8qun0dfjkxaqtq2v93xxer9vczq8v93xxeqv72xr42ca60022jqu6fu73n453tmnr0ukc0pl0t23w7eavtensjz0j2wcu7nkxhfdgp9y37welajh5kw34mq7m4xuay0a72cwec8qwgqt5vqht",
 			valid:          true,
-			decodedInvoice: &zpay32.Invoice{
+			decodedInvoice: func() *zpay32.Invoice {
+				return &zpay32.Invoice{
 					Net:         &chaincfg.MainNetParams,
 					MilliSat:    &testMillisat20mBTC,
 					Timestamp:   time.Unix(1496314658, 0),
 					PaymentHash: &testPaymentHash,
 					Description: &testPleaseConsider,
 					Destination: testPubKey,
+				}
 			},
 			skipEncoding: true, // Skip encoding since we don't have the unknown fields to encode.
 		},
@@ -164,13 +172,15 @@ func TestDecodeEncode(t *testing.T) {
 			// Ignore unknown witness version in fallback address.
 			encodedInvoice: "lnbc20m1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqhp58yjmdan79s6qqdhdzgynm4zwqd5d7xmw5fk98klysy043l2ahrqsfpppw508d6qejxtdg4y5r3zarvary0c5xw7k8txqv6x0a75xuzp0zsdzk5hq6tmfgweltvs6jk5nhtyd9uqksvr48zga9mw08667w8264gkspluu66jhtcmct36nx363km6cquhhv2cpc6q43r",
 			valid:          true,
-			decodedInvoice: &zpay32.Invoice{
+			decodedInvoice: func() *zpay32.Invoice {
+				return &zpay32.Invoice{
 					Net:             &chaincfg.MainNetParams,
 					MilliSat:        &testMillisat20mBTC,
 					Timestamp:       time.Unix(1496314658, 0),
 					PaymentHash:     &testPaymentHash,
 					DescriptionHash: &testDescriptionHash,
 					Destination:     testPubKey,
+				}
 			},
 			skipEncoding: true, // Skip encoding since we don't have the unknown fields to encode.
 		},
@@ -178,13 +188,15 @@ func TestDecodeEncode(t *testing.T) {
 			// Ignore fields with unknown lengths.
 			encodedInvoice: "lnbc241pveeq09pp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqpp3qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqhp58yjmdan79s6qqdhdzgynm4zwqd5d7xmw5fk98klysy043l2ahrqshp38yjmdan79s6qqdhdzgynm4zwqd5d7xmw5fk98klysy043l2ahnp4q0n326hr8v9zprg8gsvezcch06gfaqqhde2aj730yg0durunfhv66np3q0n326hr8v9zprg8gsvezcch06gfaqqhde2aj730yg0durunfy8huflvs2zwkymx47cszugvzn5v64ahemzzlmm62rpn9l9rm05h35aceq00tkt296289wepws9jh4499wq2l0vk6xcxffd90dpuqchqqztyayq",
 			valid:          true,
-			decodedInvoice: &zpay32.Invoice{
+			decodedInvoice: func() *zpay32.Invoice {
+				return &zpay32.Invoice{
 					Net:             &chaincfg.MainNetParams,
 					MilliSat:        &testMillisat24BTC,
 					Timestamp:       time.Unix(1503429093, 0),
 					PaymentHash:     &testPaymentHash,
 					Destination:     testPubKey,
 					DescriptionHash: &testDescriptionHash,
+				}
 			},
 			skipEncoding: true, // Skip encoding since we don't have the unknown fields to encode.
 		},
@@ -192,12 +204,14 @@ func TestDecodeEncode(t *testing.T) {
 			// Please make a donation of any amount using rhash 0001020304050607080900010203040506070809000102030405060708090102 to me @03e7156ae33b0a208d0744199163177e909e80176e55d97a2f221ede0f934dd9ad
 			encodedInvoice: "lnbc1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqdpl2pkx2ctnv5sxxmmwwd5kgetjypeh2ursdae8g6twvus8g6rfwvs8qun0dfjkxaq8rkx3yf5tcsyz3d73gafnh3cax9rn449d9p5uxz9ezhhypd0elx87sjle52x86fux2ypatgddc6k63n7erqz25le42c4u4ecky03ylcqca784w",
 			valid:          true,
-			decodedInvoice: &zpay32.Invoice{
+			decodedInvoice: func() *zpay32.Invoice {
+				return &zpay32.Invoice{
 					Net:         &chaincfg.MainNetParams,
 					Timestamp:   time.Unix(1496314658, 0),
 					PaymentHash: &testPaymentHash,
 					Description: &testPleaseConsider,
 					Destination: testPubKey,
+				}
 			},
 			beforeEncoding: func(i *zpay32.Invoice) {
 				// Since this destination pubkey was recovered
@@ -210,27 +224,31 @@ func TestDecodeEncode(t *testing.T) {
 			// Same as above, pubkey set in 'n' field.
 			encodedInvoice: "lnbc241pveeq09pp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqdqqnp4q0n326hr8v9zprg8gsvezcch06gfaqqhde2aj730yg0durunfhv66jd3m5klcwhq68vdsmx2rjgxeay5v0tkt2v5sjaky4eqahe4fx3k9sqavvce3capfuwv8rvjng57jrtfajn5dkpqv8yelsewtljwmmycq62k443",
 			valid:          true,
-			decodedInvoice: &zpay32.Invoice{
+			decodedInvoice: func() *zpay32.Invoice {
+				return &zpay32.Invoice{
 					Net:         &chaincfg.MainNetParams,
 					MilliSat:    &testMillisat24BTC,
 					Timestamp:   time.Unix(1503429093, 0),
 					PaymentHash: &testPaymentHash,
 					Destination: testPubKey,
 					Description: &testEmptyString,
+				}
 			},
 		},
 		{
 			// Please send $3 for a cup of coffee to the same peer, within 1 minute
 			encodedInvoice: "lnbc2500u1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqdq5xysxxatsyp3k7enxv4jsxqzpuaztrnwngzn3kdzw5hydlzf03qdgm2hdq27cqv3agm2awhz5se903vruatfhq77w3ls4evs3ch9zw97j25emudupq63nyw24cg27h2rspfj9srp",
 			valid:          true,
-			decodedInvoice: &zpay32.Invoice{
+			decodedInvoice: func() *zpay32.Invoice {
-				Net:         &chaincfg.MainNetParams,
+				i, _ := zpay32.NewInvoice(
-				MilliSat:    &testMillisat2500uBTC,
+					&chaincfg.MainNetParams,
-				Timestamp:   time.Unix(1496314658, 0),
+					testPaymentHash,
-				PaymentHash: &testPaymentHash,
+					time.Unix(1496314658, 0),
-				Description: &testCupOfCoffee,
+					zpay32.Amount(testMillisat2500uBTC),
-				Destination: testPubKey,
+					zpay32.Description(testCupOfCoffee),
-				Expiry:      &testExpiry60,
+					zpay32.Destination(testPubKey),
+					zpay32.Expiry(testExpiry60))
+				return i
 			},
 			beforeEncoding: func(i *zpay32.Invoice) {
 				// Since this destination pubkey was recovered
@@ -243,13 +261,15 @@ func TestDecodeEncode(t *testing.T) {
 			// Now send $24 for an entire list of things (hashed)
 			encodedInvoice: "lnbc20m1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqhp58yjmdan79s6qqdhdzgynm4zwqd5d7xmw5fk98klysy043l2ahrqscc6gd6ql3jrc5yzme8v4ntcewwz5cnw92tz0pc8qcuufvq7khhr8wpald05e92xw006sq94mg8v2ndf4sefvf9sygkshp5zfem29trqq2yxxz7",
 			valid:          true,
-			decodedInvoice: &zpay32.Invoice{
+			decodedInvoice: func() *zpay32.Invoice {
+				return &zpay32.Invoice{
 					Net:             &chaincfg.MainNetParams,
 					MilliSat:        &testMillisat20mBTC,
 					Timestamp:       time.Unix(1496314658, 0),
 					PaymentHash:     &testPaymentHash,
 					DescriptionHash: &testDescriptionHash,
 					Destination:     testPubKey,
+				}
 			},
 			beforeEncoding: func(i *zpay32.Invoice) {
 				// Since this destination pubkey was recovered
@@ -262,7 +282,8 @@ func TestDecodeEncode(t *testing.T) {
 			// The same, on testnet, with a fallback address mk2QpYatsKicvFVuTAQLBryyccRXMUaGHP
 			encodedInvoice: "lntb20m1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqhp58yjmdan79s6qqdhdzgynm4zwqd5d7xmw5fk98klysy043l2ahrqsfpp3x9et2e20v6pu37c5d9vax37wxq72un98k6vcx9fz94w0qf237cm2rqv9pmn5lnexfvf5579slr4zq3u8kmczecytdx0xg9rwzngp7e6guwqpqlhssu04sucpnz4axcv2dstmknqq6jsk2l",
 			valid:          true,
-			decodedInvoice: &zpay32.Invoice{
+			decodedInvoice: func() *zpay32.Invoice {
+				return &zpay32.Invoice{
 					Net:             &chaincfg.TestNet3Params,
 					MilliSat:        &testMillisat20mBTC,
 					Timestamp:       time.Unix(1496314658, 0),
@@ -270,6 +291,7 @@ func TestDecodeEncode(t *testing.T) {
 					DescriptionHash: &testDescriptionHash,
 					Destination:     testPubKey,
 					FallbackAddr:    testAddrTestnet,
+				}
 			},
 			beforeEncoding: func(i *zpay32.Invoice) {
 				// Since this destination pubkey was recovered
@@ -282,7 +304,8 @@ func TestDecodeEncode(t *testing.T) {
 			// On mainnet, with fallback address 1RustyRX2oai4EYYDpQGWvEL62BBGqN9T with extra routing info to get to node 029e03a901b85534ff1e92c43c74431f7ce72046060fcf7a95c37e148f78c77255
 			encodedInvoice: "lnbc20m1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqhp58yjmdan79s6qqdhdzgynm4zwqd5d7xmw5fk98klysy043l2ahrqsfpp3qjmp7lwpagxun9pygexvgpjdc4jdj85frzjq20q82gphp2nflc7jtzrcazrra7wwgzxqc8u7754cdlpfrmccae92qgzqvzq2ps8pqqqqqqqqqqqq9qqqvncsk57n4v9ehw86wq8fzvjejhv9z3w3q5zh6qkql005x9xl240ch23jk79ujzvr4hsmmafyxghpqe79psktnjl668ntaf4ne7ucs5csqh5mnnk",
 			valid:          true,
-			decodedInvoice: &zpay32.Invoice{
+			decodedInvoice: func() *zpay32.Invoice {
+				return &zpay32.Invoice{
 					Net:             &chaincfg.MainNetParams,
 					MilliSat:        &testMillisat20mBTC,
 					Timestamp:       time.Unix(1496314658, 0),
@@ -298,6 +321,7 @@ func TestDecodeEncode(t *testing.T) {
 							CltvExpDelta: 3,
 						},
 					},
+				}
 			},
 			beforeEncoding: func(i *zpay32.Invoice) {
 				// Since this destination pubkey was recovered
@@ -310,7 +334,8 @@ func TestDecodeEncode(t *testing.T) {
 			// On mainnet, with fallback address 1RustyRX2oai4EYYDpQGWvEL62BBGqN9T with extra routing info to go via nodes 029e03a901b85534ff1e92c43c74431f7ce72046060fcf7a95c37e148f78c77255 then 039e03a901b85534ff1e92c43c74431f7ce72046060fcf7a95c37e148f78c77255
 			encodedInvoice: "lnbc20m1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqhp58yjmdan79s6qqdhdzgynm4zwqd5d7xmw5fk98klysy043l2ahrqsfpp3qjmp7lwpagxun9pygexvgpjdc4jdj85fr9yq20q82gphp2nflc7jtzrcazrra7wwgzxqc8u7754cdlpfrmccae92qgzqvzq2ps8pqqqqqqqqqqqq9qqqvpeuqafqxu92d8lr6fvg0r5gv0heeeqgcrqlnm6jhphu9y00rrhy4grqszsvpcgpy9qqqqqqqqqqqq7qqzqfnlkwydm8rg30gjku7wmxmk06sevjp53fmvrcfegvwy7d5443jvyhxsel0hulkstws7vqv400q4j3wgpk4crg49682hr4scqvmad43cqd5m7tf",
 			valid:          true,
-			decodedInvoice: &zpay32.Invoice{
+			decodedInvoice: func() *zpay32.Invoice {
+				return &zpay32.Invoice{
 					Net:             &chaincfg.MainNetParams,
 					MilliSat:        &testMillisat20mBTC,
 					Timestamp:       time.Unix(1496314658, 0),
@@ -332,6 +357,7 @@ func TestDecodeEncode(t *testing.T) {
 							CltvExpDelta: 4,
 						},
 					},
+				}
 			},
 			beforeEncoding: func(i *zpay32.Invoice) {
 				// Since this destination pubkey was recovered
@@ -344,7 +370,8 @@ func TestDecodeEncode(t *testing.T) {
 			// On mainnet, with fallback (p2sh) address 3EktnHQD7RiAE6uzMj2ZifT9YgRrkSgzQX
 			encodedInvoice: "lnbc20m1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqhp58yjmdan79s6qqdhdzgynm4zwqd5d7xmw5fk98klysy043l2ahrqsfppj3a24vwu6r8ejrss3axul8rxldph2q7z9kk822r8plup77n9yq5ep2dfpcydrjwzxs0la84v3tfw43t3vqhek7f05m6uf8lmfkjn7zv7enn76sq65d8u9lxav2pl6x3xnc2ww3lqpagnh0u",
 			valid:          true,
-			decodedInvoice: &zpay32.Invoice{
+			decodedInvoice: func() *zpay32.Invoice {
+				return &zpay32.Invoice{
 					Net:             &chaincfg.MainNetParams,
 					MilliSat:        &testMillisat20mBTC,
 					Timestamp:       time.Unix(1496314658, 0),
@@ -352,6 +379,7 @@ func TestDecodeEncode(t *testing.T) {
 					DescriptionHash: &testDescriptionHash,
 					Destination:     testPubKey,
 					FallbackAddr:    testAddrMainnetP2SH,
+				}
 			},
 			beforeEncoding: func(i *zpay32.Invoice) {
 				// Since this destination pubkey was recovered
@@ -364,7 +392,8 @@ func TestDecodeEncode(t *testing.T) {
 			// On mainnet, with fallback (p2wpkh) address bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4
 			encodedInvoice: "lnbc20m1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqhp58yjmdan79s6qqdhdzgynm4zwqd5d7xmw5fk98klysy043l2ahrqsfppqw508d6qejxtdg4y5r3zarvary0c5xw7kknt6zz5vxa8yh8jrnlkl63dah48yh6eupakk87fjdcnwqfcyt7snnpuz7vp83txauq4c60sys3xyucesxjf46yqnpplj0saq36a554cp9wt865",
 			valid:          true,
-			decodedInvoice: &zpay32.Invoice{
+			decodedInvoice: func() *zpay32.Invoice {
+				return &zpay32.Invoice{
 					Net:             &chaincfg.MainNetParams,
 					MilliSat:        &testMillisat20mBTC,
 					Timestamp:       time.Unix(1496314658, 0),
@@ -372,6 +401,7 @@ func TestDecodeEncode(t *testing.T) {
 					DescriptionHash: &testDescriptionHash,
 					Destination:     testPubKey,
 					FallbackAddr:    testAddrMainnetP2WPKH,
+				}
 			},
 			beforeEncoding: func(i *zpay32.Invoice) {
 				// Since this destination pubkey was recovered
@@ -384,7 +414,8 @@ func TestDecodeEncode(t *testing.T) {
 			// On mainnet, with fallback (p2wsh) address bc1qrp33g0q5c5txsp9arysrx4k6zdkfs4nce4xj0gdcccefvpysxf3qccfmv3
 			encodedInvoice: "lnbc20m1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqhp58yjmdan79s6qqdhdzgynm4zwqd5d7xmw5fk98klysy043l2ahrqsfp4qrp33g0q5c5txsp9arysrx4k6zdkfs4nce4xj0gdcccefvpysxf3qvnjha2auylmwrltv2pkp2t22uy8ura2xsdwhq5nm7s574xva47djmnj2xeycsu7u5v8929mvuux43j0cqhhf32wfyn2th0sv4t9x55sppz5we8",
 			valid:          true,
-			decodedInvoice: &zpay32.Invoice{
+			decodedInvoice: func() *zpay32.Invoice {
+				return &zpay32.Invoice{
 					Net:             &chaincfg.MainNetParams,
 					MilliSat:        &testMillisat20mBTC,
 					Timestamp:       time.Unix(1496314658, 0),
@@ -392,6 +423,7 @@ func TestDecodeEncode(t *testing.T) {
 					DescriptionHash: &testDescriptionHash,
 					Destination:     testPubKey,
 					FallbackAddr:    testAddrMainnetP2WSH,
+				}
 			},
 			beforeEncoding: func(i *zpay32.Invoice) {
 				// Since this destination pubkey was recovered
@@ -410,7 +442,7 @@ func TestDecodeEncode(t *testing.T) {
 		}
 
 		if test.valid {
-			if err := compareInvoices(test.decodedInvoice, invoice); err != nil {
+			if err := compareInvoices(test.decodedInvoice(), invoice); err != nil {
 				t.Errorf("Invoice decoding result %d not as expected: %v", i, err)
 				return
 			}
@@ -420,12 +452,17 @@ func TestDecodeEncode(t *testing.T) {
 			continue
 		}
 
-		if test.beforeEncoding != nil {
+		var decodedInvoice *zpay32.Invoice
-			test.beforeEncoding(test.decodedInvoice)
+		if test.decodedInvoice != nil {
+			decodedInvoice = test.decodedInvoice()
 		}
 
-		if test.decodedInvoice != nil {
+		if test.beforeEncoding != nil {
-			reencoded, err := test.decodedInvoice.Encode(
+			test.beforeEncoding(decodedInvoice)
+		}
+
+		if decodedInvoice != nil {
+			reencoded, err := decodedInvoice.Encode(
 				testMessageSigner,
 			)
 			if (err == nil) != test.valid {
@@ -560,9 +597,9 @@ func compareInvoices(expected, actual *zpay32.Invoice) error {
 			*expected.DescriptionHash, *actual.DescriptionHash)
 	}
 
-	if !reflect.DeepEqual(expected.Expiry, actual.Expiry) {
+	if expected.Expiry() != actual.Expiry() {
 		return fmt.Errorf("expected expiry %d, got %d",
-			expected.Expiry, actual.Expiry)
+			expected.Expiry(), actual.Expiry())
 	}
 
 	if !reflect.DeepEqual(expected.FallbackAddr, actual.FallbackAddr) {