Added token tests

src/token/List.go

@@ -1,16 +1,24 @@
 package token
 
-import "strings"
+import (
+	"bytes"
+)
 
 // List is a slice of tokens.
 type List []Token
 
 // String implements string serialization.
 func (list List) String() string {
-	builder := strings.Builder{}
+	builder := bytes.Buffer{}
+	var last Token
 
 	for _, t := range list {
-		builder.WriteString(t.String())
+		if t.Kind == Identifier && last.Kind == Separator {
+			builder.WriteByte(' ')
+		}
+
+		builder.Write(t.Bytes)
+		last = t
 	}
 
 	return builder.String()