public void testconghaisoam()
{
maytinh call = new maytinh(this.c, this.d);
int expected = -17;
int actual = call.execute("+");
Assert.AreEqual(expected, actual);
}
public void testconghaisoduong()
{
maytinh call = new maytinh(this.a, this.b);
int expected = 15;
int actual = call.execute("+");
Assert.AreEqual(expected, actual);
}