GRAILS-6377 - improve the way the addTo method is being mocked. In particular, when a class has a hasMany that refers to a collection of its own type, don't treat the relationship as a many-to-many.

Author: jeffscottbrown

src/java/grails/test/MockUtils.groovy

@@ -825,7 +825,7 @@ class MockUtils {
                     if (otherHasMany) {
                         // many-to-many
                         otherHasMany.each { String otherCollectionName, Class otherCollectionType ->
-                            if (clazz.isAssignableFrom(otherCollectionType)) {
+                            if (clazz.isAssignableFrom(otherCollectionType) && clazz != otherCollectionType) {
                                 if (arg."$otherCollectionName" == null) {
                                     arg."$otherCollectionName" = GrailsClassUtils.createConcreteCollection(otherCollectionType)
                                 }

src/test/grails/test/MockUtilsTests.groovy

@@ -503,6 +503,21 @@ class MockUtilsTests extends GroovyTestCase {
             assertSame aliceDoeUS, relation.testDomain
         }
     }
+    
+    void testAddToWithRelationshipToSameClass() {
+        def c1 = new Company(name: 'c1')
+        def c2 = new Company(name: 'c2')
+        def c3 = new Company(name: 'c3')
+        
+        MockUtils.mockDomain (Company, [c1, c2, c3])
+        c1.addToSubsidiaries(c2)
+        c2.addToSubsidiaries(c3)
+        assertEquals 'c1 had wrong number of subsidiaries', 1, c1.subsidiaries?.size()
+        assertTrue 'c1 had wrong subsidiary', c1.subsidiaries.contains(c2)
+
+        assertEquals 'c2 had wrong number of subsidiaries', 1, c2.subsidiaries?.size()
+        assertTrue 'c2 had wrong subsidiary', c2.subsidiaries.contains(c3)
+    }
 
     /**
      * Tests the dynamically added <code>removeFrom*()</code> method.
@@ -1444,6 +1459,19 @@ class TestController  {
     }
 }
 
+class Company {
+    Long id
+    Long version
+    String name
+    static hasMany = [subsidiaries: Company]
+    static belongsTo = [parentCompany: Company]
+    Set subsidiaries
+                        
+    String toString() {
+        name
+    }
+}
+
 /**
  * Domain class used to test MockUtils.
  */