@Test
public void testValidateExpression_successful() {

    Expression expression = new Expression();
    expression.setOperator(Operator.AND);
    List<Operand> operandsList = new ArrayList<>();
    Operand operand1 = new Operand();
    Operand operand2 = new Operand();
    Operand operand3 = new Operand();
    Field field1 = new Field();
    field1.setKey("name");
    field1.setValue("sample-app");
    Field field2 = new Field();
    field2.setKey("env");
    field2.setValue("prod");
    Field field3 = new Field();
    field3.setKey("type");
    field3.setValue("gauge");
    operand1.setField(field1);
    operand2.setField(field2);
    operand3.setField(field3);
    operandsList.add(operand1);
    operandsList.add(operand2);
    expression.setOperands(operandsList);
    RequestValidator.validateExpression(expression);
}