Testing HTTP Callouts by Implementing the HttpCalloutMock Interface in Salesforce

This is a full example that shows how to test an HTTP callout. 

CalloutClass

====================

public class CalloutClass {

public static HttpResponse getInfoFromExternalService() {

HttpRequest req = new HttpRequest();

req.setEndpoint('https://example.com/example/test');

req.setMethod('GET');

Http h = new Http();

HttpResponse res = h.send(req);

return res;

}

}

JSON2ApexMock Apex Class

==============================

 @isTest

global class JSON2ApexMock implements HttpCalloutMock {

HttpResponse res;

global JSON2ApexMock(HttpResponse r)

{

res=r;

}

global HttpResponse respond(HttpRequest req){

return res;

}

}

Callout Test Class

=====================================

@isTest

private class CalloutClassTest {

@isTest static void testCallout() {

// Create a fake response

HttpResponse res=new HttpResponse();

res.setBody('{"Description": "200"}');

res.setHeader('Content-Type', 'application/json;charset=UTF-8');

res.setStatusCode(200);

// Set mock callout class

Test.setMock(HttpCalloutMock.class, new JSON2ApexMock(res));

// Call method to test.

// This causes a fake response to be sent

// from the class that implements HttpCalloutMock.

HttpResponse res = CalloutClass.getInfoFromExternalService();

// Verify response received contains fake values

String contentType = res.getHeader('Content-Type');

System.assert(contentType == 'application/json');

String actualValue = res.getBody();

String expectedValue = '{"Description":"200"}';

System.assertEquals(actualValue, expectedValue);

System.assertEquals(200, res.getStatusCode());

}

}

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