diff --git a/common/CHANGES.txt b/common/CHANGES.txt
index f97579cb2b..8eba79e71f 100644
--- a/common/CHANGES.txt
+++ b/common/CHANGES.txt
@@ -306,6 +306,9 @@ Trunk (unreleased changes)
     HADOOP-7356. RPM packages broke bin/hadoop script in developer environment.
     (Eric Yang via todd)
 
+    HADOOP-7389. Use of TestingGroups by tests causes subsequent tests to fail.
+    (atm via tomwhite)
+
 Release 0.22.0 - Unreleased
 
   INCOMPATIBLE CHANGES
diff --git a/common/src/java/org/apache/hadoop/security/UserGroupInformation.java b/common/src/java/org/apache/hadoop/security/UserGroupInformation.java
index 0b00af7ce4..45a1bad278 100644
--- a/common/src/java/org/apache/hadoop/security/UserGroupInformation.java
+++ b/common/src/java/org/apache/hadoop/security/UserGroupInformation.java
@@ -878,17 +878,21 @@ public UserGroupInformation getRealUser() {
   private static class TestingGroups extends Groups {
     private final Map<String, List<String>> userToGroupsMapping = 
       new HashMap<String,List<String>>();
+    private Groups underlyingImplementation;
     
-    private TestingGroups() {
+    private TestingGroups(Groups underlyingImplementation) {
       super(new org.apache.hadoop.conf.Configuration());
+      this.underlyingImplementation = underlyingImplementation;
     }
     
     @Override
-    public List<String> getGroups(String user) {
+    public List<String> getGroups(String user) throws IOException {
       List<String> result = userToGroupsMapping.get(user);
+      
       if (result == null) {
-        result = new ArrayList<String>();
+        result = underlyingImplementation.getGroups(user);
       }
+
       return result;
     }
 
@@ -910,7 +914,7 @@ public static UserGroupInformation createUserForTesting(String user,
     UserGroupInformation ugi = createRemoteUser(user);
     // make sure that the testing object is setup
     if (!(groups instanceof TestingGroups)) {
-      groups = new TestingGroups();
+      groups = new TestingGroups(groups);
     }
     // add the user groups
     ((TestingGroups) groups).setUserGroups(ugi.getShortUserName(), userGroups);
@@ -936,7 +940,7 @@ public static UserGroupInformation createProxyUserForTesting(String user,
     UserGroupInformation ugi = createProxyUser(user, realUser);
     // make sure that the testing object is setup
     if (!(groups instanceof TestingGroups)) {
-      groups = new TestingGroups();
+      groups = new TestingGroups(groups);
     }
     // add the user groups
     ((TestingGroups) groups).setUserGroups(ugi.getShortUserName(), userGroups);
diff --git a/common/src/test/core/org/apache/hadoop/security/TestUserGroupInformation.java b/common/src/test/core/org/apache/hadoop/security/TestUserGroupInformation.java
index afc49765ed..76d64d91fd 100644
--- a/common/src/test/core/org/apache/hadoop/security/TestUserGroupInformation.java
+++ b/common/src/test/core/org/apache/hadoop/security/TestUserGroupInformation.java
@@ -62,6 +62,29 @@ public class TestUserGroupInformation {
         + "DEFAULT");
     UserGroupInformation.setConfiguration(conf);
   }
+  
+  /** Test login method */
+  @Test
+  public void testLogin() throws Exception {
+    // login from unix
+    UserGroupInformation ugi = UserGroupInformation.getCurrentUser();
+    assertEquals(UserGroupInformation.getCurrentUser(),
+                 UserGroupInformation.getLoginUser());
+    assertTrue(ugi.getGroupNames().length >= 1);
+
+    // ensure that doAs works correctly
+    UserGroupInformation userGroupInfo = 
+      UserGroupInformation.createUserForTesting(USER_NAME, GROUP_NAMES);
+    UserGroupInformation curUGI = 
+      userGroupInfo.doAs(new PrivilegedExceptionAction<UserGroupInformation>(){
+        public UserGroupInformation run() throws IOException {
+          return UserGroupInformation.getCurrentUser();
+        }});
+    // make sure in the scope of the doAs, the right user is current
+    assertEquals(curUGI, userGroupInfo);
+    // make sure it is not the same as the login user
+    assertFalse(curUGI.equals(UserGroupInformation.getLoginUser()));
+  }
 
   /**
    * given user name - get all the groups.
@@ -107,29 +130,6 @@ public Object run() throws IOException {
       }});
   }
 
-  /** Test login method */
-  @Test
-  public void testLogin() throws Exception {
-    // login from unix
-    UserGroupInformation ugi = UserGroupInformation.getCurrentUser();
-    assertEquals(UserGroupInformation.getCurrentUser(),
-                 UserGroupInformation.getLoginUser());
-    assertTrue(ugi.getGroupNames().length >= 1);
-
-    // ensure that doAs works correctly
-    UserGroupInformation userGroupInfo = 
-      UserGroupInformation.createUserForTesting(USER_NAME, GROUP_NAMES);
-    UserGroupInformation curUGI = 
-      userGroupInfo.doAs(new PrivilegedExceptionAction<UserGroupInformation>(){
-        public UserGroupInformation run() throws IOException {
-          return UserGroupInformation.getCurrentUser();
-        }});
-    // make sure in the scope of the doAs, the right user is current
-    assertEquals(curUGI, userGroupInfo);
-    // make sure it is not the same as the login user
-    assertFalse(curUGI.equals(UserGroupInformation.getLoginUser()));
-  }
-
   /** test constructor */
   @Test
   public void testConstructor() throws Exception {