Testing Integrations

public class ShippingRateService {
    public Decimal getRate(String postalCode) {
        HttpRequest request = new HttpRequest();
        request.setEndpoint('callout:Shipping_API/rates?postal=' + postalCode);
        request.setMethod('GET');

        HttpResponse response = new Http().send(request);

        if (response.getStatusCode() != 200) {
            throw new CalloutException('Shipping API returned status ' + response.getStatusCode());
        }

        Map<String, Object> parsed = (Map<String, Object>) JSON.deserializeUntyped(response.getBody());
        return (Decimal) parsed.get('rate');
    }
}

This combines nearly every lesson from this module: a Named Credential endpoint (Lesson 5), an HttpRequest/HttpResponse callout (Lesson 4), and JSON parsing (Lesson 2) — a genuinely realistic integration, ready to test.

@isTest
public class ShippingRateMock implements HttpCalloutMock {
    public HttpResponse respond(HttpRequest request) {
        HttpResponse response = new HttpResponse();
        response.setStatusCode(200);
        response.setBody('{"rate": 45.50}');
        return response;
    }
}

@isTest
private class ShippingRateServiceTest {
    @isTest
    static void getRateReturnsParsedValue() {
        Test.setMock(HttpCalloutMock.class, new ShippingRateMock());

        Test.startTest();
        Decimal rate = new ShippingRateService().getRate('8001');
        Test.stopTest();

        System.assertEquals(45.50, rate);
    }
}

This is exactly Module 31's "Mocking HTTP Callouts" lesson, now testing genuinely real integration logic instead of an isolated example — the mock, the assertion, and the specific-value habit from Module 31 all directly applied.

@isTest
public class ShippingRateFailureMock implements HttpCalloutMock {
    public HttpResponse respond(HttpRequest request) {
        HttpResponse response = new HttpResponse();
        response.setStatusCode(500);
        response.setBody('Internal Server Error');
        return response;
    }
}

@isTest
static void getRateThrowsOnServerError() {
    Test.setMock(HttpCalloutMock.class, new ShippingRateFailureMock());

    try {
        new ShippingRateService().getRate('8001');
        System.assert(false, 'Expected a CalloutException');
    } catch (CalloutException e) {
        System.assert(e.getMessage().contains('500'));
    }
}

This is Module 31's exception-testing pattern (the try/System.assert(false)/catch shape) combined with Module 31's failure-mock pattern — confirming the throw new CalloutException(...) guard in getRate actually fires correctly on a real 500 response.