Test with Mocks

@isTest
public class PaymentGatewaySuccessMock implements HttpCalloutMock {
    public HttpResponse respond(HttpRequest request) {
        HttpResponse response = new HttpResponse();
        response.setStatusCode(200);
        response.setBody('{"transactionId": "txn_123"}');
        return response;
    }
}

@isTest
private class ProcessPaymentJobTest {
    @isTest
    static void successfulPaymentMarksOrderPaid() {
        Order__c order = new Order__c(Total__c = 500, Payment_Token__c = 'tok_abc');
        insert order;

        Test.setMock(HttpCalloutMock.class, new PaymentGatewaySuccessMock());

        Test.startTest();
        System.enqueueJob(new ProcessPaymentJob(order.Id, 500, 'tok_abc', 1));
        Test.stopTest(); // forces the Queueable job to actually run before this line returns

        Order__c updated = [SELECT Status__c, Payment_Reference__c FROM Order__c WHERE Id = :order.Id];
        System.assertEquals('Paid', updated.Status__c);
        System.assertEquals('txn_123', updated.Payment_Reference__c);
    }
}

1. @isTest — marks the mock class.
2. public class PaymentGatewaySuccessMock implements HttpCalloutMock { — Module 36's mocking interface.
3. public HttpResponse respond(HttpRequest request) { — the required method.
4. HttpResponse response = new HttpResponse(); — a fabricated response.
5. response.setStatusCode(200); — a successful status.
6. response.setBody('{"transactionId": "txn_123"}'); — a fabricated success body.
7. return response; — hands it back.
8. } — closes the method.
9. } — closes the mock class.
10. (blank line)
11. @isTest — marks the test class.
12. private class ProcessPaymentJobTest { — the test class.
13. @isTest — marks the test method.
14. static void successfulPaymentMarksOrderPaid() { — states what's verified.
15. Order__c order = new Order__c(Total__c = 500, Payment_Token__c = 'tok_abc'); — test data.
16. insert order; — saves it.
17. (blank line)
18. Test.setMock(HttpCalloutMock.class, new PaymentGatewaySuccessMock()); — swaps in the fabricated success response.
19. (blank line)
20. Test.startTest(); — the governor-limit boundary.
21. System.enqueueJob(new ProcessPaymentJob(order.Id, 500, 'tok_abc', 1)); — enqueues the job under test.
22. Test.stopTest(); // forces the Queueable job to actually run before this line returns — Module 31's boundary, doing double duty here.
23. (blank line)
24. Order__c updated = [SELECT Status__c, Payment_Reference__c FROM Order__c WHERE Id = :order.Id]; — re-queries the record after the job has run.
25. System.assertEquals('Paid', updated.Status__c); — a specific expected status.
26. System.assertEquals('txn_123', updated.Payment_Reference__c); — a specific expected reference.
27. } — closes the test method.
28. } — closes the test class.

Test.stopTest() (Module 31) does double duty here — it forces the Queueable job to run synchronously to completion, meaning the assertion afterward can safely check the result of the async work, not just that it was enqueued.

@isTest
public class PaymentGatewayDeclineMock implements HttpCalloutMock {
    public HttpResponse respond(HttpRequest request) {
        HttpResponse response = new HttpResponse();
        response.setStatusCode(402);
        response.setBody('{"reason": "Insufficient funds"}');
        return response;
    }
}

@isTest
static void declinedPaymentMarksOrderDeclined() {
    Order__c order = new Order__c(Total__c = 500, Payment_Token__c = 'tok_abc');
    insert order;

    Test.setMock(HttpCalloutMock.class, new PaymentGatewayDeclineMock());

    Test.startTest();
    System.enqueueJob(new ProcessPaymentJob(order.Id, 500, 'tok_abc', 1));
    Test.stopTest();

    Order__c updated = [SELECT Status__c, Decline_Reason__c FROM Order__c WHERE Id = :order.Id];
    System.assertEquals('Payment Declined', updated.Status__c);
    System.assertEquals('Insufficient funds', updated.Decline_Reason__c);
}

1. @isTest — marks the mock class.
2. public class PaymentGatewayDeclineMock implements HttpCalloutMock { — a second, separate mock.
3. public HttpResponse respond(HttpRequest request) { — the required method.
4. HttpResponse response = new HttpResponse(); — a fabricated response.
5. response.setStatusCode(402); — the gateway's decline status.
6. response.setBody('{"reason": "Insufficient funds"}'); — a fabricated decline reason.
7. return response; — hands it back.
8. } — closes the method.
9. } — closes the mock class.
10. (blank line)
11. @isTest — marks the test method.
12. static void declinedPaymentMarksOrderDeclined() { — states what's verified.
13. Order__c order = new Order__c(Total__c = 500, Payment_Token__c = 'tok_abc'); — test data.
14. insert order; — saves it.
15. (blank line)
16. Test.setMock(HttpCalloutMock.class, new PaymentGatewayDeclineMock()); — swaps in the decline mock.
17. (blank line)
18. Test.startTest(); — the boundary.
19. System.enqueueJob(new ProcessPaymentJob(order.Id, 500, 'tok_abc', 1)); — enqueues the job.
20. Test.stopTest(); — forces it to run.
21. (blank line)
22. Order__c updated = [SELECT Status__c, Decline_Reason__c FROM Order__c WHERE Id = :order.Id]; — re-queries the record.
23. System.assertEquals('Payment Declined', updated.Status__c); — confirms the correct final status.
24. System.assertEquals('Insufficient funds', updated.Decline_Reason__c); — confirms the specific reason was captured.
25. } — closes the test method.

This confirms 402 gets routed correctly through Lesson 2's status-code branching all the way to the final Order__c status — the full chain, exercised end to end.

@isTest
public class PaymentGatewayErrorMock implements HttpCalloutMock {
    public HttpResponse respond(HttpRequest request) {
        HttpResponse response = new HttpResponse();
        response.setStatusCode(500);
        return response;
    }
}

@isTest
static void thirdFailedAttemptGivesUpWithPaymentError() {
    Order__c order = new Order__c(Total__c = 500, Payment_Token__c = 'tok_abc');
    insert order;

    Test.setMock(HttpCalloutMock.class, new PaymentGatewayErrorMock());

    Test.startTest();
    System.enqueueJob(new ProcessPaymentJob(order.Id, 500, 'tok_abc', 3)); // already the 3rd attempt
    Test.stopTest();

    Order__c updated = [SELECT Status__c FROM Order__c WHERE Id = :order.Id];
    System.assertEquals('Payment Error', updated.Status__c);
}

1. @isTest — marks the mock class.
2. public class PaymentGatewayErrorMock implements HttpCalloutMock { — a third mock, simulating a technical failure.
3. public HttpResponse respond(HttpRequest request) { — the required method.
4. HttpResponse response = new HttpResponse(); — a fabricated response.
5. response.setStatusCode(500); — an error status, neither success nor decline.
6. return response; — hands it back.
7. } — closes the method.
8. } — closes the mock class.
9. (blank line)
10. @isTest — marks the test method.
11. static void thirdFailedAttemptGivesUpWithPaymentError() { — states the exact boundary under test.
12. Order__c order = new Order__c(Total__c = 500, Payment_Token__c = 'tok_abc'); — test data.
13. insert order; — saves it.
14. (blank line)
15. Test.setMock(HttpCalloutMock.class, new PaymentGatewayErrorMock()); — swaps in the error mock.
16. (blank line)
17. Test.startTest(); — the boundary.
18. System.enqueueJob(new ProcessPaymentJob(order.Id, 500, 'tok_abc', 3)); // already the 3rd attempt — starts directly at the retry limit, rather than simulating all three attempts.
19. Test.stopTest(); — forces it to run.
20. (blank line)
21. Order__c updated = [SELECT Status__c FROM Order__c WHERE Id = :order.Id]; — re-queries the record.
22. System.assertEquals('Payment Error', updated.Status__c); — confirms the job gave up rather than chaining a fourth attempt.
23. } — closes the test method.

Starting at attemptNumber = 3 (the limit) directly, rather than simulating all three attempts, tests Lesson 4's boundary condition precisely — confirming the job gives up and records Payment Error instead of chaining a fourth attempt.