Grails integration test not recognising controller save method

I recently upgraded a project from 2.2 to 2.4.4, and upgraded the integration tests by replacing

IntegrationTest extends GroovyTestCase 

with

@TestMixin(IntegrationTestMixin) 

My controllers have save methods e.g. :

class IssueController {

    def save() { 
        ...
        if (!issueService.save(issue)) { 
            render(view: "create", model: [issueInstance: issue]) 
            return 
        } 
    }

and the integration test (in test/integration) :

@Before 
void setUp() { 
    ic = new IssueController() 
} 

@Test 
void testValidSave() { 

    ic.params.issueNo = "test" 

    ic.save() 
        assert ic.flash.successAlert ==  "Saved issue test" 
        assert ic.response.redirectUrl == '/issue/list' 
    }

but my Integrations tests, when calling ic.save() don't call the controller save method (and so fail). If I rename the save() method to say saveIt(), and the call to ic.saveIt(), everything works fine

but I don't want to have to rename all my controller method names.