Fix unit test, it should return after any error is returned from Decode

function whether expected or not, rather than continue and try to
compare invalid decoded results.

Extend the unit test slightly to check the header.

Remove go-test/deep dependency in favour of standard library reflect
package.

function_call.go

@@ -6,10 +6,10 @@ import (
 	"github.com/jackc/pgio"
 )
 
-type FunctionCall struct{
-	Function uint32
-	ArgFormatCodes []uint16
-	Arguments [][]byte
+type FunctionCall struct {
+	Function         uint32
+	ArgFormatCodes   []uint16
+	Arguments        [][]byte
 	ResultFormatCode uint16
 }
 
@@ -24,9 +24,9 @@ func (dst *FunctionCall) Decode(src []byte) error {
 	// Specifies the object ID of the function to call.
 	dst.Function = binary.BigEndian.Uint32(src[rp:])
 	rp += 4
-	// The number of argument format codes that follow (denoted C below). 
-	// This can be zero to indicate that there are no arguments or that the arguments all use the default format (text); 
-	// or one, in which case the specified format code is applied to all arguments; 
+	// The number of argument format codes that follow (denoted C below).
+	// This can be zero to indicate that there are no arguments or that the arguments all use the default format (text);
+	// or one, in which case the specified format code is applied to all arguments;
 	// or it can equal the actual number of arguments.
 	nArgumentCodes := int(binary.BigEndian.Uint16(src[rp:]))
 	rp += 2
@@ -37,36 +37,36 @@ func (dst *FunctionCall) Decode(src []byte) error {
 		if ac != 0 && ac != 1 {
 			return &invalidMessageFormatErr{messageType: "FunctionCall"}
 		}
-        argumentCodes[i] = ac
-        rp += 2
-    }
+		argumentCodes[i] = ac
+		rp += 2
+	}
 	dst.ArgFormatCodes = argumentCodes
-	
+
 	// Specifies the number of arguments being supplied to the function.
 	nArguments := int(binary.BigEndian.Uint16(src[rp:]))
 	rp += 2
 	arguments := make([][]byte, nArguments)
 	for i := 0; i < nArguments; i++ {
-		// The length of the argument value, in bytes (this count does not include itself). Can be zero. 
+		// The length of the argument value, in bytes (this count does not include itself). Can be zero.
 		// As a special case, -1 indicates a NULL argument value. No value bytes follow in the NULL case.
-        argumentLength := int(binary.BigEndian.Uint32(src[rp:]))
-        rp += 4
-        if argumentLength == -1 {
+		argumentLength := int(binary.BigEndian.Uint32(src[rp:]))
+		rp += 4
+		if argumentLength == -1 {
 			arguments[i] = nil
 		} else {
 			// The value of the argument, in the format indicated by the associated format code. n is the above length.
-			argumentValue := src[rp:rp+argumentLength]
+			argumentValue := src[rp : rp+argumentLength]
 			rp += argumentLength
 			arguments[i] = argumentValue
-        }
-    }
+		}
+	}
 	dst.Arguments = arguments
 	// The format code for the function result. Must presently be zero (text) or one (binary).
 	resultFormatCode := binary.BigEndian.Uint16(src[rp:])
 	if resultFormatCode != 0 && resultFormatCode != 1 {
-        return &invalidMessageFormatErr{messageType: "FunctionCall"}
-    }
-	dst.ResultFormatCode  = resultFormatCode
+		return &invalidMessageFormatErr{messageType: "FunctionCall"}
+	}
+	dst.ResultFormatCode = resultFormatCode
 	return nil
 }
 
@@ -78,17 +78,17 @@ func (src *FunctionCall) Encode(dst []byte) []byte {
 	dst = pgio.AppendUint32(dst, src.Function)
 	dst = pgio.AppendUint16(dst, uint16(len(src.ArgFormatCodes)))
 	for _, argFormatCode := range src.ArgFormatCodes {
-        dst = pgio.AppendUint16(dst, argFormatCode)
-    }
+		dst = pgio.AppendUint16(dst, argFormatCode)
+	}
 	dst = pgio.AppendUint16(dst, uint16(len(src.Arguments)))
 	for _, argument := range src.Arguments {
-        if argument == nil {
-            dst = pgio.AppendInt32(dst, -1)
-        } else {
-            dst = pgio.AppendInt32(dst, int32(len(argument)))
-            dst = append(dst, argument...)
-        }
-    }
+		if argument == nil {
+			dst = pgio.AppendInt32(dst, -1)
+		} else {
+			dst = pgio.AppendInt32(dst, int32(len(argument)))
+			dst = append(dst, argument...)
+		}
+	}
 	dst = pgio.AppendUint16(dst, src.ResultFormatCode)
 	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
 	return dst