@Test
public void testEqualsObject() {

    Expression expression = new Expression("hello", "there");
    Expression expression2 = new Expression("hello", "there");
    assertEquals(expression, expression2);
    expression2 = new Expression("hello", "there2");
    assertFalse(expression.equals(expression2));
    expression2 = new Expression("hello");
    assertFalse(expression.equals(expression2));
    expression = new Expression("hello");
    assertEquals(expression, expression2);
}