remove unnecessary for loop in token signing string for readability (#34)

* remove unnecessary for loop in token signing string for readability

 - add testcase
 - add benchmark
 - improve performance slightly

* Fix benchtests on token_test.go

* Update token_test.go to v4

Co-authored-by: hyeonjae <hyeonjae@ip-192-168-1-3.ap-northeast-2.compute.internal>
Co-authored-by: Luis Gabriel Gomez <lggomez@users.noreply.github.com>

token.go

@@ -74,22 +74,19 @@ func (t *Token) SignedString(key interface{}) (string, error) {
 // the SignedString.
 func (t *Token) SigningString() (string, error) {
 	var err error
-	parts := make([]string, 2)
-	for i := range parts {
-		var jsonValue []byte
-		if i == 0 {
-			if jsonValue, err = json.Marshal(t.Header); err != nil {
-				return "", err
-			}
-		} else {
-			if jsonValue, err = json.Marshal(t.Claims); err != nil {
-				return "", err
-			}
-		}
+	var jsonValue []byte
 
-		parts[i] = EncodeSegment(jsonValue)
+	if jsonValue, err = json.Marshal(t.Header); err != nil {
+		return "", err
 	}
-	return strings.Join(parts, "."), nil
+	header := EncodeSegment(jsonValue)
+
+	if jsonValue, err = json.Marshal(t.Claims); err != nil {
+		return "", err
+	}
+	claim := EncodeSegment(jsonValue)
+
+	return strings.Join([]string{header, claim}, "."), nil
 }
 
 // Parse parses, validates, verifies the signature and returns the parsed token.

token_test.go

@@ -0,0 +1,79 @@
+package jwt_test
+
+import (
+	"testing"
+
+	"github.com/golang-jwt/jwt/v4"
+)
+
+func TestToken_SigningString(t1 *testing.T) {
+	type fields struct {
+		Raw       string
+		Method    jwt.SigningMethod
+		Header    map[string]interface{}
+		Claims    jwt.Claims
+		Signature string
+		Valid     bool
+	}
+	tests := []struct {
+		name    string
+		fields  fields
+		want    string
+		wantErr bool
+	}{
+		{
+			name: "",
+			fields: fields{
+				Raw:    "",
+				Method: jwt.SigningMethodHS256,
+				Header: map[string]interface{}{
+					"typ": "JWT",
+					"alg": jwt.SigningMethodHS256.Alg(),
+				},
+				Claims:    jwt.StandardClaims{},
+				Signature: "",
+				Valid:     false,
+			},
+			want: "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.e30",
+			wantErr: false,
+		},
+	}
+	for _, tt := range tests {
+		t1.Run(tt.name, func(t1 *testing.T) {
+			t := &jwt.Token{
+				Raw:       tt.fields.Raw,
+				Method:    tt.fields.Method,
+				Header:    tt.fields.Header,
+				Claims:    tt.fields.Claims,
+				Signature: tt.fields.Signature,
+				Valid:     tt.fields.Valid,
+			}
+			got, err := t.SigningString()
+			if (err != nil) != tt.wantErr {
+				t1.Errorf("SigningString() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if got != tt.want {
+				t1.Errorf("SigningString() got = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func BenchmarkToken_SigningString(b *testing.B) {
+	t := &jwt.Token{
+		Method:    jwt.SigningMethodHS256,
+		Header: map[string]interface{}{
+			"typ": "JWT",
+			"alg": jwt.SigningMethodHS256.Alg(),
+		},
+		Claims:    jwt.StandardClaims{},
+	}
+	b.Run("BenchmarkToken_SigningString", func(b *testing.B) {
+		b.ResetTimer()
+		b.ReportAllocs()
+		for i := 0; i<b.N; i++ {
+			t.SigningString()
+		}
+	})
+}