Add negative tests for WriteMessage.

This commit adds tests for the error paths when writing a message
to the wire.

fakemessage_test.go

@@ -5,14 +5,16 @@
 package btcwire_test
 
 import (
+	"github.com/conformal/btcwire"
 	"io"
 )
 
 // fakeMessage implements the btcwire.Message interface and is used to force
-// errors.
+// encode errors in messages.
 type fakeMessage struct {
-	command    string
+	command        string
-	maxPayload uint32
+	payload        []byte
+	forceEncodeErr bool
 }
 
 // BtcDecode doesn't do anything.  It just satisfies the btcwire.Message
@@ -21,10 +23,20 @@ func (msg *fakeMessage) BtcDecode(r io.Reader, pver uint32) error {
 	return nil
 }
 
-// BtcEncode doesn't do anything.  It just satisfies the btcwire.Message
+// BtcEncode writes the payload field of the fake message or forces an error
-// interface.
+// if the forceEncodeErr flag of the fake message is set.  It also satisfies the
+// btcwire.Message interface.
 func (msg *fakeMessage) BtcEncode(w io.Writer, pver uint32) error {
-	return nil
+	if msg.forceEncodeErr {
+		err := &btcwire.MessageError{
+			Func:        "fakeMessage.BtcEncode",
+			Description: "intentional error",
+		}
+		return err
+	}
+
+	_, err := w.Write(msg.payload)
+	return err
 }
 
 // Command returns the command field of the fake message and satisfies the
@@ -33,8 +45,8 @@ func (msg *fakeMessage) Command() string {
 	return msg.command
 }
 
-// Command returns the maxPayload field of the fake message and satisfies the
+// MaxPayloadLength simply returns 0.  It is only here to satisfy the
 // btcwire.Message interface.
 func (msg *fakeMessage) MaxPayloadLength(pver uint32) uint32 {
-	return msg.maxPayload
+	return 0
 }

message_test.go

@@ -303,3 +303,66 @@ func TestReadMessageWireErrors(t *testing.T) {
 		}
 	}
 }
+
+// TestWriteMessageWireErrors performs negative tests against wire encoding from
+// concrete messages to confirm error paths work correctly.
+func TestWriteMessageWireErrors(t *testing.T) {
+	pver := btcwire.ProtocolVersion
+	btcnet := btcwire.MainNet
+	btcwireErr := &btcwire.MessageError{}
+
+	// Fake message with a command that is too long.
+	badCommandMsg := &fakeMessage{command: "somethingtoolong"}
+
+	// Fake message with a problem during encoding
+	encodeErrMsg := &fakeMessage{forceEncodeErr: true}
+
+	// Fake message that has a payload which exceed max.
+	exceedPayload := make([]byte, btcwire.MaxMessagePayload+1)
+	exceedPayloadErrMsg := &fakeMessage{payload: exceedPayload}
+
+	bogusPayload := []byte{0x01, 0x02, 0x03, 0x04}
+	bogusMsg := &fakeMessage{command: "bogus", payload: bogusPayload}
+
+	tests := []struct {
+		msg    btcwire.Message    // Message to encode
+		pver   uint32             // Protocol version for wire encoding
+		btcnet btcwire.BitcoinNet // Bitcoin network for wire encoding
+		max    int                // Max size of fixed buffer to induce errors
+		err    error              // Expected error
+	}{
+		// Command too long.
+		{badCommandMsg, pver, btcnet, 0, btcwireErr},
+		// Force error in payload encode.
+		{encodeErrMsg, pver, btcnet, 0, btcwireErr},
+		// Force error due to exceeding max payload size.
+		{exceedPayloadErrMsg, pver, btcnet, 0, btcwireErr},
+		// Force error in header write.
+		{bogusMsg, pver, btcnet, 0, io.ErrShortWrite},
+		// Force error in payload write.
+		{bogusMsg, pver, btcnet, 24, io.ErrShortWrite},
+	}
+
+	t.Logf("Running %d tests", len(tests))
+	for i, test := range tests {
+		// Encode wire format.
+		w := newFixedWriter(test.max)
+		err := btcwire.WriteMessage(w, test.msg, test.pver, test.btcnet)
+		if reflect.TypeOf(err) != reflect.TypeOf(test.err) {
+			t.Errorf("WriteMessage #%d wrong error got: %v <%T>, "+
+				"want: %T", i, err, err, test.err)
+			continue
+		}
+
+		// For errors which are not of type btcwire.MessageError, check
+		// them for equality.
+		if _, ok := err.(*btcwire.MessageError); !ok {
+			if err != test.err {
+				t.Errorf("ReadMessage #%d wrong error got: %v <%T>, "+
+					"want: %v <%T>", i, err, err,
+					test.err, test.err)
+				continue
+			}
+		}
+	}
+}

test_coverage.txt

@@ -1,74 +1,75 @@
 
 github.com/conformal/btcwire/message.go		 ReadMessage				 100.00% (37/37)
+github.com/conformal/btcwire/message.go		 WriteMessage				 100.00% (27/27)
 github.com/conformal/btcwire/msgtx.go		 MsgTx.Copy				 100.00% (24/24)
 github.com/conformal/btcwire/common.go		 readVarInt				 100.00% (24/24)
 github.com/conformal/btcwire/message.go		 makeEmptyMessage			 100.00% (20/20)
 github.com/conformal/btcwire/netaddress.go	 readNetAddress				 100.00% (20/20)
 github.com/conformal/btcwire/msggetheaders.go	 MsgGetHeaders.BtcDecode		 100.00% (19/19)
 github.com/conformal/btcwire/msggetblocks.go	 MsgGetBlocks.BtcDecode			 100.00% (19/19)
-github.com/conformal/btcwire/msggetblocks.go	 MsgGetBlocks.BtcEncode			 100.00% (18/18)
 github.com/conformal/btcwire/msggetheaders.go	 MsgGetHeaders.BtcEncode		 100.00% (18/18)
+github.com/conformal/btcwire/msggetblocks.go	 MsgGetBlocks.BtcEncode			 100.00% (18/18)
 github.com/conformal/btcwire/msgheaders.go	 MsgHeaders.BtcDecode			 100.00% (16/16)
 github.com/conformal/btcwire/common.go		 writeVarInt				 100.00% (16/16)
+github.com/conformal/btcwire/msgheaders.go	 MsgHeaders.BtcEncode			 100.00% (15/15)
 github.com/conformal/btcwire/shahash.go		 NewShaHashFromStr			 100.00% (15/15)
 github.com/conformal/btcwire/msgaddr.go		 MsgAddr.BtcEncode			 100.00% (15/15)
-github.com/conformal/btcwire/msgheaders.go	 MsgHeaders.BtcEncode			 100.00% (15/15)
 github.com/conformal/btcwire/netaddress.go	 writeNetAddress			 100.00% (14/14)
 github.com/conformal/btcwire/msginv.go		 MsgInv.BtcDecode			 100.00% (13/13)
-github.com/conformal/btcwire/msgnotfound.go	 MsgNotFound.BtcDecode			 100.00% (13/13)
 github.com/conformal/btcwire/msggetdata.go	 MsgGetData.BtcDecode			 100.00% (13/13)
 github.com/conformal/btcwire/msgaddr.go		 MsgAddr.BtcDecode			 100.00% (13/13)
-github.com/conformal/btcwire/msgnotfound.go	 MsgNotFound.BtcEncode			 100.00% (12/12)
+github.com/conformal/btcwire/msgnotfound.go	 MsgNotFound.BtcDecode			 100.00% (13/13)
-github.com/conformal/btcwire/protocol.go	 ServiceFlag.String			 100.00% (12/12)
 github.com/conformal/btcwire/msggetdata.go	 MsgGetData.BtcEncode			 100.00% (12/12)
 github.com/conformal/btcwire/msginv.go		 MsgInv.BtcEncode			 100.00% (12/12)
-github.com/conformal/btcwire/blockheader.go	 readBlockHeader			 100.00% (10/10)
+github.com/conformal/btcwire/msgnotfound.go	 MsgNotFound.BtcEncode			 100.00% (12/12)
+github.com/conformal/btcwire/protocol.go	 ServiceFlag.String			 100.00% (12/12)
 github.com/conformal/btcwire/message.go		 discardInput				 100.00% (10/10)
+github.com/conformal/btcwire/blockheader.go	 readBlockHeader			 100.00% (10/10)
 github.com/conformal/btcwire/msgblock.go	 MsgBlock.BtcDecode			 100.00% (10/10)
 github.com/conformal/btcwire/msgblock.go	 MsgBlock.BtcEncode			 100.00% (9/9)
+github.com/conformal/btcwire/msgalert.go	 MsgAlert.BtcDecode			 100.00% (8/8)
 github.com/conformal/btcwire/msgalert.go	 MsgAlert.BtcEncode			 100.00% (8/8)
 github.com/conformal/btcwire/common.go		 readVarString				 100.00% (8/8)
-github.com/conformal/btcwire/msgalert.go	 MsgAlert.BtcDecode			 100.00% (8/8)
 github.com/conformal/btcwire/blockheader.go	 writeBlockHeader			 100.00% (8/8)
-github.com/conformal/btcwire/msgversion.go	 NewMsgVersionFromConn			 100.00% (7/7)
-github.com/conformal/btcwire/common.go		 DoubleSha256				 100.00% (7/7)
-github.com/conformal/btcwire/msgpong.go		 MsgPong.BtcDecode			 100.00% (7/7)
-github.com/conformal/btcwire/msgpong.go		 MsgPong.BtcEncode			 100.00% (7/7)
 github.com/conformal/btcwire/common.go		 randomUint64				 100.00% (7/7)
-github.com/conformal/btcwire/message.go		 readMessageHeader			 100.00% (7/7)
+github.com/conformal/btcwire/msgversion.go	 NewMsgVersionFromConn			 100.00% (7/7)
+github.com/conformal/btcwire/msgpong.go		 MsgPong.BtcDecode			 100.00% (7/7)
+github.com/conformal/btcwire/common.go		 DoubleSha256				 100.00% (7/7)
 github.com/conformal/btcwire/common.go		 writeVarString				 100.00% (7/7)
-github.com/conformal/btcwire/common.go		 writeElements				 100.00% (5/5)
+github.com/conformal/btcwire/msgpong.go		 MsgPong.BtcEncode			 100.00% (7/7)
-github.com/conformal/btcwire/msgheaders.go	 MsgHeaders.AddBlockHeader		 100.00% (5/5)
+github.com/conformal/btcwire/message.go		 readMessageHeader			 100.00% (7/7)
-github.com/conformal/btcwire/msginv.go		 MsgInv.AddInvVect			 100.00% (5/5)
-github.com/conformal/btcwire/shahash.go		 ShaHash.SetBytes			 100.00% (5/5)
-github.com/conformal/btcwire/msgnotfound.go	 MsgNotFound.AddInvVect			 100.00% (5/5)
-github.com/conformal/btcwire/msgping.go		 MsgPing.BtcDecode			 100.00% (5/5)
-github.com/conformal/btcwire/msgping.go		 MsgPing.BtcEncode			 100.00% (5/5)
-github.com/conformal/btcwire/common.go		 readElements				 100.00% (5/5)
 github.com/conformal/btcwire/netaddress.go	 NewNetAddress				 100.00% (5/5)
+github.com/conformal/btcwire/msgping.go		 MsgPing.BtcEncode			 100.00% (5/5)
+github.com/conformal/btcwire/shahash.go		 ShaHash.SetBytes			 100.00% (5/5)
+github.com/conformal/btcwire/msgping.go		 MsgPing.BtcDecode			 100.00% (5/5)
+github.com/conformal/btcwire/common.go		 readElements				 100.00% (5/5)
+github.com/conformal/btcwire/msgnotfound.go	 MsgNotFound.AddInvVect			 100.00% (5/5)
 github.com/conformal/btcwire/msggetblocks.go	 MsgGetBlocks.AddBlockLocatorHash	 100.00% (5/5)
-github.com/conformal/btcwire/msggetdata.go	 MsgGetData.AddInvVect			 100.00% (5/5)
+github.com/conformal/btcwire/common.go		 writeElements				 100.00% (5/5)
 github.com/conformal/btcwire/shahash.go		 NewShaHash				 100.00% (5/5)
-github.com/conformal/btcwire/msgaddr.go		 MsgAddr.AddAddress			 100.00% (5/5)
+github.com/conformal/btcwire/msggetdata.go	 MsgGetData.AddInvVect			 100.00% (5/5)
+github.com/conformal/btcwire/msginv.go		 MsgInv.AddInvVect			 100.00% (5/5)
 github.com/conformal/btcwire/msggetheaders.go	 MsgGetHeaders.AddBlockLocatorHash	 100.00% (5/5)
+github.com/conformal/btcwire/msgheaders.go	 MsgHeaders.AddBlockHeader		 100.00% (5/5)
 github.com/conformal/btcwire/msgaddr.go		 MsgAddr.AddAddresses			 100.00% (5/5)
-github.com/conformal/btcwire/msgmempool.go	 MsgMemPool.BtcEncode			 100.00% (4/4)
+github.com/conformal/btcwire/msgaddr.go		 MsgAddr.AddAddress			 100.00% (5/5)
-github.com/conformal/btcwire/msgpong.go		 MsgPong.MaxPayloadLength		 100.00% (4/4)
 github.com/conformal/btcwire/invvect.go		 writeInvVect				 100.00% (4/4)
-github.com/conformal/btcwire/shahash.go		 ShaHash.String				 100.00% (4/4)
 github.com/conformal/btcwire/invvect.go		 readInvVect				 100.00% (4/4)
+github.com/conformal/btcwire/shahash.go		 ShaHash.String				 100.00% (4/4)
 github.com/conformal/btcwire/msgping.go		 MsgPing.MaxPayloadLength		 100.00% (4/4)
+github.com/conformal/btcwire/msgmempool.go	 MsgMemPool.BtcEncode			 100.00% (4/4)
 github.com/conformal/btcwire/netaddress.go	 maxNetAddressPayload			 100.00% (4/4)
+github.com/conformal/btcwire/msgpong.go		 MsgPong.MaxPayloadLength		 100.00% (4/4)
 github.com/conformal/btcwire/msgmempool.go	 MsgMemPool.BtcDecode			 100.00% (4/4)
-github.com/conformal/btcwire/shahash.go		 ShaHash.Bytes				 100.00% (3/3)
-github.com/conformal/btcwire/invvect.go		 InvType.String				 100.00% (3/3)
-github.com/conformal/btcwire/error.go		 MessageError.Error			 100.00% (3/3)
-github.com/conformal/btcwire/msgversion.go	 MsgVersion.HasService			 100.00% (3/3)
 github.com/conformal/btcwire/msgblock.go	 MsgBlock.AddTransaction		 100.00% (3/3)
 github.com/conformal/btcwire/msgaddr.go		 MsgAddr.MaxPayloadLength		 100.00% (3/3)
+github.com/conformal/btcwire/msgversion.go	 MsgVersion.HasService			 100.00% (3/3)
+github.com/conformal/btcwire/invvect.go		 InvType.String				 100.00% (3/3)
+github.com/conformal/btcwire/shahash.go		 ShaHash.Bytes				 100.00% (3/3)
 github.com/conformal/btcwire/netaddress.go	 NetAddress.HasService			 100.00% (3/3)
-github.com/conformal/btcwire/netaddress.go	 NetAddress.SetAddress			 100.00% (2/2)
+github.com/conformal/btcwire/error.go		 MessageError.Error			 100.00% (3/3)
 github.com/conformal/btcwire/msgblock.go	 MsgBlock.ClearTransactions		 100.00% (2/2)
+github.com/conformal/btcwire/netaddress.go	 NetAddress.SetAddress			 100.00% (2/2)
 github.com/conformal/btcwire/msgalert.go	 MsgAlert.Command			 100.00% (1/1)
 github.com/conformal/btcwire/blockheader.go	 NewBlockHeader				 100.00% (1/1)
 github.com/conformal/btcwire/common.go		 readElement				 100.00% (1/1)
@@ -141,13 +142,12 @@ github.com/conformal/btcwire/msgtx.go		 MsgTx.BtcEncode			 78.26% (18/23)
 github.com/conformal/btcwire/msgtx.go		 readTxIn				 76.47% (13/17)
 github.com/conformal/btcwire/msgtx.go		 readTxOut				 75.00% (9/12)
 github.com/conformal/btcwire/blockheader.go	 BlockHeader.BlockSha			 75.00% (6/8)
-github.com/conformal/btcwire/msgtx.go		 writeOutPoint				 75.00% (3/4)
 github.com/conformal/btcwire/msgtx.go		 readOutPoint				 75.00% (3/4)
+github.com/conformal/btcwire/msgtx.go		 writeOutPoint				 75.00% (3/4)
 github.com/conformal/btcwire/msgtx.go		 writeTxIn				 73.33% (11/15)
 github.com/conformal/btcwire/msgtx.go		 writeTxOut				 72.73% (8/11)
-github.com/conformal/btcwire/message.go		 WriteMessage				 70.00% (21/30)
 github.com/conformal/btcwire/msgversion.go	 MsgVersion.BtcDecode			 68.00% (17/25)
 github.com/conformal/btcwire/msgversion.go	 MsgVersion.BtcEncode			 63.64% (14/22)
 github.com/conformal/btcwire/msgblock.go	 MsgBlock.BtcDecodeTxLoc		 0.00% (0/16)
-github.com/conformal/btcwire			 ---------------------------------	 92.39% (862/933)
+github.com/conformal/btcwire			 ---------------------------------	 93.33% (868/930)