Why do methods defined as testmethod do not support web service callouts?
I have been struggling with this error for a few days now. I get this error every time I try to run a test for a method that has an httpCallout. I followed the architecture from http://www.salesforce.com/us/developer/docs/apexcode/Content/apex_classes_restful_http_testing_httpcalloutmock.htm, but to no avail. I thought it could be something I was messing up in my code, so I copied all three of the classes from the documentation, and I am still getting the error when I try to run the test. All of the classes are on Salesforce API 29. Has anyone run into this before?
The answer to your question - why methods defined as testmethod do not support web service callouts is - You need to call Test.setMock(...) in your test class once you've implemented the required interfaces to prevent this particular error message. You shouldn't need to use Test.isRunningTest() to test your call outs (and doing so gives you untestable code).
Answer (1)
In Salesforce, methods defined as @testMethod (or testMethod keyword prior to API version 26.0) are part of Apex test classes and are used for unit testing. These methods are primarily designed to test the behavior of Apex code in a controlled environment, typically within the Salesforce platform itself.
One important aspect of unit testing in Salesforce is that the code being tested should not make any real HTTP callouts to external web services. This is to ensure that unit tests are isolated and predictable, without depending on external factors such as network connectivity or the availability of external services.
To enforce this rule, Salesforce prohibits making web service callouts from methods defined as @testMethod. If you attempt to make a web service callout from a test method, Salesforce will throw a "callout not allowed from test code" error.
Instead, Salesforce provides a mechanism for simulating web service callouts in unit tests using mock callouts. You can create mock callout classes that implement the HttpCalloutMock interface to simulate the response from external web services. This allows you to test how your code behaves when making callouts without actually invoking the external service during testing.
By using mock callouts, you can ensure that your unit tests remain isolated and independent of external dependencies while still testing the behavior of your code that interacts with web services. This approach promotes robust and reliable testing practices within the Salesforce platform.