@@ -534,9 +534,15 @@ def create_thread(self):
         new = Thread(self)
         return new
 
-    # iterating through a Column is the same as iterating
-    # through its list of rows.
-    def __iter__(self): return self.rows.__iter__()
+    def next_row(self, row):
+        if row is None:
+            return self.rows[0]
+
+        index = self.rows.index(row)
+        try:
+            return self.rows[index+1]
+        except IndexError:
+            return None
 
 
 class TopColumn(Column):
@@ -648,9 +654,6 @@ def __init__(self, column, name=None):
         self.sync.register(self)
         self.start()
 
-    def get_column(self):
-        return self.column
-
     def __str__(self):
         return '<' + self.name + '>'
 
@@ -668,9 +671,11 @@ def dequeue(self):
 
     def jump_to(self, row):
         """Removes this thread from its current row and moves it to row."""
-        self.row.remove_thread(self)
+        if self.row:
+            self.row.remove_thread(self)
         self.row = row
-        self.row.add_thread(self)
+        if self.row:
+            self.row.add_thread(self)
 
     def balk(self):
         self.row.remove_thread(self)
@@ -679,7 +684,6 @@ def balk(self):
     def start(self):
         """Moves this thread to the top of the column."""
         self.queued = False
-        self.iter = self.column.__iter__()
         self.row = None
         self.next_loop()
 
@@ -694,17 +698,8 @@ def next_row(self):
         if self.queued:
             return
 
-        if self.row:
-            self.row.remove_thread(self)
-        else:
-            # this probably means we executed balk
-            self.iter = self.column.__iter__()
-
-        try:
-            self.row = self.iter.next()
-            self.row.add_thread(self)
-        except StopIteration:
-            self.row = None
+        row = self.column.next_row(self.row)
+        self.jump_to(row)
 
     def skip_body(self):
         """Skips the body of a conditional."""
 
@@ -11,12 +11,12 @@
 
 class Tests(unittest.TestCase):
 
-    def xtest_sync_mutex(self):
+    def test_sync_mutex(self):
         sync = Sync.Sync(['mutex.py'])
 
         threads = sync.get_threads()
         threadA = threads[0]
-        column = threadA.get_column()
+        column = threadA.column
 
         source = threadA.step()
         self.assertEqual(source, 'mutex.wait()')
@@ -42,7 +42,7 @@ def xtest_sync_mutex(self):
         source = threadA.exec_line('pid = pid()', sync)
         self.assertEqual(sync.locals['pid'], 'A')
 
-    def xtest_sync_conditional(self):
+    def test_sync_conditional(self):
         sync = Sync.Sync(['sync_code/conditional.py'])
         threads = sync.get_threads()
         threadA = threads[0]
@@ -90,7 +90,10 @@ def test_sync_while(self):
         self.assertEqual(source, '    counter += 1')
 
         source = threadA.step()
-        print source
+        self.assertEqual(source, 'while counter < 1:')
+
+        source = threadA.step()
+        self.assertEqual(source, 'pass')
 
 
 if __name__ == '__main__':