Can I create/update/delete metadata using APEX?

Question

In particular, I want to create a custom field for Task for a specific unit test, then delete that field when the test is finished.

I know Salesforce uses the Metadata API, but this seems designed to be used externally (via REST or SOAP web services).

I am also aware that there is a separate development, APEX Metadata API, that allows us to access said API via Apex (by making Web service calls!): https://github.com/financialforcedev/apex-mdapi

Is there a way of calling into the Metadata API natively? Or, to make the problem scope smaller, can I create/delete custom Task fields via APEX?

Thanks

Edit: there seems to be some confusion as to why I want to do this. Basically, I'm creating a managed package, which can be installed by different customers in their respective orgs. Each and every org will be customised in a different way, so I cannot make any assumption as to what these customisations will be.

What I want to test is how a certain part of my code that deals with tasks will behave in the presence of some custom fields. That is why I wanted to create a field, run my code, then delete the field, in the context of a unit test.

I considered the question answered, as 2 people have come back to me telling me that I cannot modify metadata from APEX.

Answer 1

The Apex testing framework is built to test functionality implemented in Apex.

But there is a lot more functionality in an org than just Apex, so a natural extension of this test functionality is to want to begin to test other functionality. In some cases, the natural features of the Apex test framework align quite closely.

Take for example workflow actions like field updates and assigning tasks. Because these are both data-oriented features, you could easily test the functionality of those features.

But many features do not align with Apex test functionality, most especially configuration/metadata changes.

Furthermore, the testing framework works primarily in the context of the runtime transaction model and is designed to leave no footprint either inside of the org (ringfencing of real data, no commits to data changes, and automatic rollback of DML) and in systems that are integrated with the org (no callouts allowed).

I think the tests you propose are a very good idea. I just think you will need to use an external testing framework to do so. With greater and greater support of config changes in the metadata and tooling API, these kinds of processes are becoming easier to automate.

Perhaps you could adapt your existing build process to perform this test. In other words after you deploy to your sandbox/trialforce org, automate a follow on process to deploy some metadata changes and then rerun all tests.

Answer 2

You can not modify metadata using test classes.

Metadata class invoke web-service so, to imitate the request and response you should use Mock classes. Basically, you are writing a test class for web-service.

Create a new Mock class and implement required response there using Test.setMock.

Ex: A sample test class:

@isTest

private class WebSvcCalloutTest {
    @isTest static void testEchoString() {              
        // This causes a fake response to be generated
        Test.setMock(WebServiceMock.class, new WebServiceMockImpl());

        // Call the method that invokes a callout
        String output = WebSvcCallout.callEchoString('Hello World!');

        // Verify that a fake result is returned
        System.assertEquals('Mock response', output); 
    }
}

A Sample Mock class to imitate the response:

@isTest

global class WebServiceMockImpl implements WebServiceMock {
   global void doInvoke(
           Object stub,
           Object request,
           Map<String, Object> response,
           String endpoint,
           String soapAction,
           String requestName,
           String responseNS,
           String responseName,
           String responseType) {
       docSample.EchoStringResponse_element respElement = 
           new docSample.EchoStringResponse_element();
       respElement.EchoStringResult = 'Mock response';
       response.put('response_x', respElement); 
   }
}

This way you can get required response in main class using during unit test run and your code can perform further. Reference: https://www.salesforce.com/us/developer/docs/apexcode/Content/apex_callouts_wsdl2apex_testing.htm

Also, if there is situation where you are checking for deleted field in main class then you can use Test.isRunningTest()