Improvements

parsing/cliargs.go

@@ -0,0 +1,28 @@
+package parsing
+
+import (
+	"errors"
+	"math/big"
+	"os"
+)
+
+type Cliargs struct {
+	value *big.Int
+}
+
+func (arg *Cliargs) Parse() (*big.Int, error) {
+	args := os.Args[1:]
+	if len(args) != 1 {
+		return nil, errors.New("only expected 1 arg")
+	}
+	num, success := new(big.Int).SetString(args[0], 10)
+	if !success {
+		return nil, errors.New("argument is not an integer")
+	}
+	arg.value = num
+	return num, nil
+}
+
+func (arg *Cliargs) GetNumber() *big.Int {
+	return arg.value
+}

parsing/cliargs_test.go

@@ -0,0 +1,44 @@
+package parsing
+
+import (
+	"math/big"
+	"os"
+	"testing"
+)
+
+func TestCliargs_Parse(t *testing.T) {
+	tests := []struct {
+		name    string
+		args    []string
+		want    *big.Int
+		wantErr bool
+	}{
+		{
+			name:    "Test with valid integer",
+			args:    []string{"", "10"}, // the first argument is the program name
+			want:    big.NewInt(10),
+			wantErr: false,
+		},
+		{
+			name:    "Test with non-integer",
+			args:    []string{"", "abc"}, // the first argument is the program name
+			want:    nil,
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			os.Args = tt.args
+			parser := &Cliargs{}
+			got, err := parser.Parse()
+			if (err != nil) != tt.wantErr {
+				t.Errorf("Parse() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !tt.wantErr && got.Cmp(tt.want) != 0 {
+				t.Errorf("Parse() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

parsing/interface.go

@@ -0,0 +1,7 @@
+package parsing
+
+import "math/big"
+
+type Parser interface {
+	Parse() (*big.Int, error)
+}