commit 19cce29fe9dd43cdb019a2d0e50b252cde8ebbb1
Author: Trang Truong Thi Huyen <trang.truong@pyramid-consulting.com>
Date:   Mon May 11 13:29:43 2015 +0700

    MAGNOLIA-6097: Fix review by throwning an IllegalArgumentException Instead of returning null in case of exception

diff --git a/magnolia-core/src/main/java/info/magnolia/cms/security/MgnlGroupManager.java b/magnolia-core/src/main/java/info/magnolia/cms/security/MgnlGroupManager.java
index 509eaba..e8447f0 100644
--- a/magnolia-core/src/main/java/info/magnolia/cms/security/MgnlGroupManager.java
+++ b/magnolia-core/src/main/java/info/magnolia/cms/security/MgnlGroupManager.java
@@ -303,8 +303,7 @@ public class MgnlGroupManager extends RepositoryBackedSecurityManager implements
         try {
             super.remove(group.getName(), groupName, NODE_GROUPS);
         } catch (PrincipalNotFoundException e) {
-            // group doesn't exist in this UM
-            return null;
+            throw new IllegalArgumentException("group doesn't exist in this GM" + e);
         }
         return getGroup(group.getName());
     }
@@ -314,8 +313,7 @@ public class MgnlGroupManager extends RepositoryBackedSecurityManager implements
         try {
             super.remove(group.getName(), roleName, NODE_ROLES);
         } catch (PrincipalNotFoundException e) {
-            // group doesn't exist in this UM
-            return null;
+            throw new IllegalArgumentException("role doesn't exist in this GM" + e);
         }
         return getGroup(group.getName());
     }

commit a1681e21814980f258ade9be7ff628db032530cb
Author: Trang Truong Thi Huyen <trang.truong@pyramid-consulting.com>
Date:   Thu May 7 13:53:01 2015 +0700

    MAGNOLIA-6097: provide removeGroup() and removeRole() methods

diff --git a/magnolia-core/src/main/java/info/magnolia/cms/security/GroupManager.java b/magnolia-core/src/main/java/info/magnolia/cms/security/GroupManager.java
index 02ef782..658dc35 100644
--- a/magnolia-core/src/main/java/info/magnolia/cms/security/GroupManager.java
+++ b/magnolia-core/src/main/java/info/magnolia/cms/security/GroupManager.java
@@ -99,4 +99,17 @@ public interface GroupManager {
      */
     public Collection<String> getGroupsWithRole(String roleName);
 
+    /**
+     * Removes group from a group.
+     *
+     * @return group object with the group assignment removed.
+     */
+    public Group removeGroup(Group group, String groupName) throws AccessDeniedException;
+
+    /**
+     * Removes role from a group.
+     *
+     * @return group object without removed role.
+     */
+    public Group removeRole(Group group, String roleName) throws AccessDeniedException;
 }
diff --git a/magnolia-core/src/main/java/info/magnolia/cms/security/MgnlGroupManager.java b/magnolia-core/src/main/java/info/magnolia/cms/security/MgnlGroupManager.java
index e4ce1fe..509eaba 100644
--- a/magnolia-core/src/main/java/info/magnolia/cms/security/MgnlGroupManager.java
+++ b/magnolia-core/src/main/java/info/magnolia/cms/security/MgnlGroupManager.java
@@ -297,4 +297,26 @@ public class MgnlGroupManager extends RepositoryBackedSecurityManager implements
             }
         });
     }
+
+    @Override
+    public Group removeGroup(Group group, String groupName) throws AccessDeniedException {
+        try {
+            super.remove(group.getName(), groupName, NODE_GROUPS);
+        } catch (PrincipalNotFoundException e) {
+            // group doesn't exist in this UM
+            return null;
+        }
+        return getGroup(group.getName());
+    }
+
+    @Override
+    public Group removeRole(Group group, String roleName) throws AccessDeniedException {
+        try {
+            super.remove(group.getName(), roleName, NODE_ROLES);
+        } catch (PrincipalNotFoundException e) {
+            // group doesn't exist in this UM
+            return null;
+        }
+        return getGroup(group.getName());
+    }
 }
diff --git a/magnolia-core/src/test/java/info/magnolia/cms/security/MgnlGroupTest.java b/magnolia-core/src/test/java/info/magnolia/cms/security/MgnlGroupTest.java
index 434a06b..d494f7a 100644
--- a/magnolia-core/src/test/java/info/magnolia/cms/security/MgnlGroupTest.java
+++ b/magnolia-core/src/test/java/info/magnolia/cms/security/MgnlGroupTest.java
@@ -158,4 +158,32 @@ public class MgnlGroupTest {
         final Collection<String> groupsD= gman.getAllGroups("groupD");
         assertEquals(0, groupsD.size());
     }
+
+    @Test
+    public void testRemoveGroup() throws Exception {
+
+        // GIVEN
+        Group groupA = gman.getGroup("groupA");
+
+        // WHEN
+        gman.addGroup(groupA, "groupB");
+        gman.removeGroup(groupA, "groupB");
+
+        // THEN
+        assertFalse(gman.getGroup("groupA").getGroups().contains("groupB"));
+    }
+
+    @Test
+    public void testRemoveRole() throws Exception {
+
+        // GIVEN
+        Group groupA = gman.getGroup("groupA");
+
+        // THEN
+        gman.addRole(groupA, "roleW");
+        gman.removeRole(groupA, "roleW");
+
+        // THEN
+        assertFalse(gman.getGroup("groupA").getRoles().contains("roleW"));
+    }
 }