dcrutil: Use mock addr params in tests.

This implements a mock address params struct that implements the new
interface and modifies the test code to make use of the mock params
instead of chaincfg.  This completely decouples the tests, with the
exception of the example code, from chaincfg and therefore any updates
to it such as introducing new test networks will not require changes to
the tests.

dcrutil/address_test.go

@@ -13,13 +13,108 @@ import (
 	"testing"
 
 	"github.com/decred/base58"
-	"github.com/decred/dcrd/chaincfg"
 	"github.com/decred/dcrd/chaincfg/chainec"
 	"github.com/decred/dcrd/dcrec"
 	"github.com/decred/dcrd/dcrec/secp256k1"
 	"golang.org/x/crypto/ripemd160"
 )
 
+// mockAddrParams implements the AddressParams interface and is used throughout
+// the tests to mock multiple networks.
+type mockAddrParams struct {
+	pubKeyID     [2]byte
+	pkhEcdsaID   [2]byte
+	pkhEd25519ID [2]byte
+	pkhSchnorrID [2]byte
+	scriptHashID [2]byte
+	privKeyID    [2]byte
+}
+
+// AddrIDPubKeyV0 returns the magic prefix bytes associated with the mock params
+// for version 0 pay-to-pubkey addresses.
+//
+// This is part of the AddressParams interface.
+func (p *mockAddrParams) AddrIDPubKeyV0() [2]byte {
+	return p.pubKeyID
+}
+
+// AddrIDPubKeyHashECDSAV0 returns the magic prefix bytes associated with the
+// mock params for version 0 pay-to-pubkey-hash addresses where the underlying
+// pubkey is secp256k1 and the signature algorithm is ECDSA.
+//
+// This is part of the AddressParams interface.
+func (p *mockAddrParams) AddrIDPubKeyHashECDSAV0() [2]byte {
+	return p.pkhEcdsaID
+}
+
+// AddrIDPubKeyHashEd25519V0 returns the magic prefix bytes associated with the
+// mock params for version 0 pay-to-pubkey-hash addresses where the underlying
+// pubkey and signature algorithm are Ed25519.
+//
+// This is part of the AddressParams interface.
+func (p *mockAddrParams) AddrIDPubKeyHashEd25519V0() [2]byte {
+	return p.pkhEd25519ID
+}
+
+// AddrIDPubKeyHashSchnorrV0 returns the magic prefix bytes associated with the
+// mock params for version 0 pay-to-pubkey-hash addresses where the underlying
+// pubkey is secp256k1 and the signature algorithm is Schnorr.
+//
+// This is part of the AddressParams interface.
+func (p *mockAddrParams) AddrIDPubKeyHashSchnorrV0() [2]byte {
+	return p.pkhSchnorrID
+}
+
+// AddrIDScriptHashV0 returns the magic prefix bytes associated with the mock
+// params for version 0 pay-to-script-hash addresses.
+//
+// This is part of the AddressParams interface.
+func (p *mockAddrParams) AddrIDScriptHashV0() [2]byte {
+	return p.scriptHashID
+}
+
+// mockMainNetParams returns mock mainnet address parameters to use throughout
+// the tests.  They match the Decred mainnet params as of the time this comment
+// was written.
+func mockMainNetParams() *mockAddrParams {
+	return &mockAddrParams{
+		pubKeyID:     [2]byte{0x13, 0x86}, // starts with Dk
+		pkhEcdsaID:   [2]byte{0x07, 0x3f}, // starts with Ds
+		pkhEd25519ID: [2]byte{0x07, 0x1f}, // starts with De
+		pkhSchnorrID: [2]byte{0x07, 0x01}, // starts with DS
+		scriptHashID: [2]byte{0x07, 0x1a}, // starts with Dc
+		privKeyID:    [2]byte{0x22, 0xde}, // starts with Pm
+	}
+}
+
+// mockTestNetParams returns mock testnet address parameters to use throughout
+// the tests.  They match the Decred mainnet params as of the time this comment
+// was written.
+func mockTestNetParams() *mockAddrParams {
+	return &mockAddrParams{
+		pubKeyID:     [2]byte{0x28, 0xf7}, // starts with Tk
+		pkhEcdsaID:   [2]byte{0x0f, 0x21}, // starts with Ts
+		pkhEd25519ID: [2]byte{0x0f, 0x01}, // starts with Te
+		pkhSchnorrID: [2]byte{0x0e, 0xe3}, // starts with TS
+		scriptHashID: [2]byte{0x0e, 0xfc}, // starts with Tc
+		privKeyID:    [2]byte{0x23, 0x0e}, // starts with Pt
+	}
+}
+
+// mockRegNetParams returns mock regression test address parameters to use
+// throughout the tests.  They match the Decred mainnet params as of the time
+// this comment was written.
+func mockRegNetParams() *mockAddrParams {
+	return &mockAddrParams{
+		pubKeyID:     [2]byte{0x25, 0xe5}, // starts with Rk
+		pkhEcdsaID:   [2]byte{0x0e, 0x00}, // starts with Rs
+		pkhEd25519ID: [2]byte{0x0d, 0xe0}, // starts with Re
+		pkhSchnorrID: [2]byte{0x0d, 0xc2}, // starts with RS
+		scriptHashID: [2]byte{0x0d, 0xdb}, // starts with Rc
+		privKeyID:    [2]byte{0x22, 0xfe}, // starts with Pr
+	}
+}
+
 // tstAddressPubKey makes an AddressPubKey, setting the unexported fields with
 // the parameters.
 func tstAddressPubKey(serializedPubKey []byte, pubKeyFormat PubKeyFormat, netID [2]byte) *AddressSecpPubKey {
@@ -32,9 +127,9 @@ func tstAddressPubKey(serializedPubKey []byte, pubKeyFormat PubKeyFormat, netID
 }
 
 func TestAddresses(t *testing.T) {
-	mainNetParams := &chaincfg.MainNetParams
-	testNetParams := &chaincfg.TestNet3Params
-	regNetParams := &chaincfg.RegNetParams
+	mainNetParams := mockMainNetParams()
+	testNetParams := mockTestNetParams()
+	regNetParams := mockRegNetParams()
 	tests := []struct {
 		name    string
 		addr    string