math/big: clean up *Int encoding tests

- more uniform naming
- test sign more deliberately
- remove superfluous test (JSON encoder always uses the JSON marshaler if present)

Change-Id: I37b1e367c01fc8bae1e06adbdb72dd366c08d5ce
Reviewed-on: https://go-review.googlesource.com/15110Reviewed-by: Alan Donovan <adonovan@google.com>

src/math/big/intmarsh.go

@@ -59,6 +59,10 @@ func (z *Int) UnmarshalText(text []byte) error {
 	return nil
 }
 
+// The JSON marshallers are only here for API backward compatibility
+// (programs that explicitly look for these two methods). JSON works
+// fine with the TextMarshaler only.
+
 // MarshalJSON implements the json.Marshaler interface.
 func (x *Int) MarshalJSON() ([]byte, error) {
 	return x.MarshalText()

src/math/big/intmarsh_test.go

@@ -13,16 +13,11 @@ import (
 )
 
 var encodingTests = []string{
-	"-539345864568634858364538753846587364875430589374589",
-	"-678645873",
-	"-100",
-	"-2",
-	"-1",
 	"0",
 	"1",
 	"2",
 	"10",
-	"42",
+	"1000",
 	"1234567890",
 	"298472983472983471903246121093472394872319615612417471234712061",
 }
@@ -32,9 +27,11 @@ func TestIntGobEncoding(t *testing.T) {
 	enc := gob.NewEncoder(&medium)
 	dec := gob.NewDecoder(&medium)
 	for _, test := range encodingTests {
+		for _, sign := range []string{"", "+", "-"} {
+			x := sign + test
 			medium.Reset() // empty buffer for each test case (in case of failures)
 			var tx Int
-		tx.SetString(test, 10)
+			tx.SetString(x, 10)
 			if err := enc.Encode(&tx); err != nil {
 				t.Errorf("encoding of %s failed: %s", &tx, err)
 				continue
@@ -48,6 +45,7 @@ func TestIntGobEncoding(t *testing.T) {
 				t.Errorf("transmission of %s failed: got %s want %s", &tx, &rx, &tx)
 			}
 		}
+	}
 }
 
 // Sending a nil Int pointer (inside a slice) on a round trip through gob should yield a zero.
@@ -78,8 +76,10 @@ func TestGobEncodingNilIntInSlice(t *testing.T) {
 
 func TestIntJSONEncoding(t *testing.T) {
 	for _, test := range encodingTests {
+		for _, sign := range []string{"", "+", "-"} {
+			x := sign + test
 			var tx Int
-		tx.SetString(test, 10)
+			tx.SetString(x, 10)
 			b, err := json.Marshal(&tx)
 			if err != nil {
 				t.Errorf("marshaling of %s failed: %s", &tx, err)
@@ -94,44 +94,15 @@ func TestIntJSONEncoding(t *testing.T) {
 				t.Errorf("JSON encoding of %s failed: got %s want %s", &tx, &rx, &tx)
 			}
 		}
-}
-
-var intVals = []string{
-	"-141592653589793238462643383279502884197169399375105820974944592307816406286",
-	"-1415926535897932384626433832795028841971",
-	"-141592653589793",
-	"-1",
-	"0",
-	"1",
-	"141592653589793",
-	"1415926535897932384626433832795028841971",
-	"141592653589793238462643383279502884197169399375105820974944592307816406286",
-}
-
-func TestIntJSONEncodingTextMarshaller(t *testing.T) {
-	for _, num := range intVals {
-		var tx Int
-		tx.SetString(num, 0)
-		b, err := json.Marshal(&tx)
-		if err != nil {
-			t.Errorf("marshaling of %s failed: %s", &tx, err)
-			continue
-		}
-		var rx Int
-		if err := json.Unmarshal(b, &rx); err != nil {
-			t.Errorf("unmarshaling of %s failed: %s", &tx, err)
-			continue
-		}
-		if rx.Cmp(&tx) != 0 {
-			t.Errorf("JSON encoding of %s failed: got %s want %s", &tx, &rx, &tx)
-		}
 	}
 }
 
-func TestIntXMLEncodingTextMarshaller(t *testing.T) {
-	for _, num := range intVals {
+func TestIntXMLEncoding(t *testing.T) {
+	for _, test := range encodingTests {
+		for _, sign := range []string{"", "+", "-"} {
+			x := sign + test
 			var tx Int
-		tx.SetString(num, 0)
+			tx.SetString(x, 0)
 			b, err := xml.Marshal(&tx)
 			if err != nil {
 				t.Errorf("marshaling of %s failed: %s", &tx, err)
@@ -146,4 +117,5 @@ func TestIntXMLEncodingTextMarshaller(t *testing.T) {
 				t.Errorf("XML encoding of %s failed: got %s want %s", &tx, &rx, &tx)
 			}
 		}
+	}
 }