How to catch an Exception with Spock

How to use Spock library

First of all, Spock is a unit-testing library which is usually used with Grails and Groovy. So you have to import the spock dependency in the Build.groovy or Pom.xml:

‘org.spockframework:spock-core:1.0-groovy-2.4’

group: ‘cglib’, name: ‘cglib-nodep’, version: ‘2.2.2’

(* Cglib library, it is necessary for mocking objects)

How to catch Exceptions with Spock

With Spock you can check everything you think, but in this article we are going to focus on Exception and its management.

In addition, you can catch an exception as follows:

 void "paymentService throws ServiceException if paymentId is null"(){
        given: "An external payment service"
        PaymentService paymentService = new PaymentService()
        PaymentExternalService paymentExternalService = Mock(PaymentExternalService)
        and:"it receives a paymentId null"
        Long paymentIdNull = null
        paymentExternalService.retrievePaymentInfo(paymentIdNull) >> {throw new Exception()}
        when:
        paymentService.retrievePaymentInfo(paymentIdNull)
        then:
        thrown ExternalServiceException
    }

void "paymentService throws ServiceException if paymentId is null"(){

given: "An external payment service"

PaymentService paymentService = new PaymentService()

PaymentExternalService paymentExternalService = Mock(PaymentExternalService)

and:"it receives a paymentId null"

Long paymentIdNull = null

paymentExternalService.retrievePaymentInfo(paymentIdNull) >> {throw new Exception()}

when:

paymentService.retrievePaymentInfo(paymentIdNull)

then:

thrown ExternalServiceException

}

In the test code you can see, the external service has been mocked in order to throw a NullPointerException, so our Payment service catch it and it will throw the final ExternalServiceException, as follows:

package test.service

class PaymentService {

    PaymentExternalService paymentExternalService

    List retrievePaymentInfo(Long paymentId) throws ExternalServiceException{
        List paymentsInfo = []
        try{
            paymentsInfo = paymentExternalService.retrievePaymentInfo(paymentExternalService)
        }catch (Exception exception){
            throw new ExternalServiceException("External Payment Error","PaymentService","Payment")
        }
        paymentsInfo
    }

}

package test.service

class PaymentService {

PaymentExternalService paymentExternalService

List retrievePaymentInfo(Long paymentId) throws ExternalServiceException{

List paymentsInfo = []

try{

paymentsInfo = paymentExternalService.retrievePaymentInfo(paymentExternalService)

}catch (Exception exception){

throw new ExternalServiceException("External Payment Error","PaymentService","Payment")

}

paymentsInfo

}

It is very common, the customer exception thrown has some attributes, for example:

package test.service

class ExternalServiceException extends Exception {
    private String operation
    private String service
    ExternalServiceException (String message, String operationAfected, String serviceThrownError){
        super(message)
        operation = operationAfected
        service = serviceThrownError
    }

    String getOperation() {
        operation
    }

    String getService() {
        service
    }
}

package test.service

class ExternalServiceException extends Exception {

private String operation

private String service

ExternalServiceException (String message, String operationAfected, String serviceThrownError){

super(message)

operation = operationAfected

service = serviceThrownError

}

String getOperation() {

operation

}

String getService() {

service

}

How to check Exception attributes’

Threfore, you would be able to check all of the attributes which the Exception thrown had, as follows:

 void "paymentService throws ServiceException whose operation is PaymentService and Date is the current moment if paymentId is null"(){
        given: "An external payment service"
        PaymentService paymentService = new PaymentService()
        PaymentExternalService paymentExternalService = Mock(PaymentExternalService)
        and:"it receives a paymentId null"
        Long paymentIdNull = null
        paymentExternalService.retrievePaymentInfo(paymentIdNull) >> {throw new Exception()}
        when:
        paymentService.retrievePaymentInfo(paymentIdNull)
        then:
        final ExternalServiceException externalPaymentServiceException = thrown()
        "PaymentService" == externalPaymentServiceException.getOperation()
        "Payment" == externalPaymentServiceException.getService()
    }

void "paymentService throws ServiceException whose operation is PaymentService and Date is the current moment if paymentId is null"(){

given: "An external payment service"

PaymentService paymentService = new PaymentService()

PaymentExternalService paymentExternalService = Mock(PaymentExternalService)

and:"it receives a paymentId null"

Long paymentIdNull = null

paymentExternalService.retrievePaymentInfo(paymentIdNull) >> {throw new Exception()}

when:

paymentService.retrievePaymentInfo(paymentIdNull)

then:

final ExternalServiceException externalPaymentServiceException = thrown()

"PaymentService" == externalPaymentServiceException.getOperation()

"Payment" == externalPaymentServiceException.getService()

}

You can read other interesting articles like Defensive Programming and Resilient Systems. Also you can visit another interesting blogs like Mrhaki’s blog.

Best Regards