diff --git a/data_structures/binary_tree/binary_search_tree.py b/data_structures/binary_tree/binary_search_tree.py
index ce490fd98524..c65c71795657 100644
--- a/data_structures/binary_tree/binary_search_tree.py
+++ b/data_structures/binary_tree/binary_search_tree.py
@@ -152,7 +152,8 @@ def inorder(self, arr: list, node: Node):
     def find_kth_smallest(self, k: int, node: Node) -> int:
         """Return the kth smallest element in a binary search tree"""
         arr: list = []
-        self.inorder(arr, node)  # append all values to list using inorder traversal
+        # append all values to list using inorder traversal
+        self.inorder(arr, node)
         return arr[k - 1]
 
 
@@ -186,36 +187,35 @@ def binary_search_tree():
     Traceback (most recent call last):
     ...
     IndexError: Warning: Tree is empty! please use another.
+    >>> t = BinarySearchTree().insert(8, 3, 6, 1, 10, 14, 13, 4, 7)
+    >>> t.search(6)
+    {'6': (4, 7)}
+    >>> t.search(-1)
+    >>> print(t.root.value)
+    8
+    >>> print(t)
+    {'8': ({'3': (1, {'6': (4, 7)})}, {'10': (None, {'14': (13, None)})})}
+    >>> t.get_max().value
+    14
+    >>> t.get_min().value
+    1
+    >>> t.find_kth_smallest(k=2,node=t.root)
+    3
+    >>> t.find_kth_smallest(k=5,node=t.root)
+    7
+    >>> t.remove(7)
+    >>> print(" ".join(repr(i.value) for i in t.traversal_tree()))
+    8 3 1 6 4 10 14 13
+    >>> t.remove(10)
+    >>> print(" ".join(repr(i.value) for i in t.traversal_tree()))
+    8 3 1 6 4 14 13
+    >>> t.remove(14)
+    >>> print(" ".join(repr(i.value) for i in t.traversal_tree()))
+    8 3 1 6 4 13
     """
-    testlist = (8, 3, 6, 1, 10, 14, 13, 4, 7)
-    t = BinarySearchTree()
-    for i in testlist:
-        t.insert(i)
-
-    # Prints all the elements of the list in order traversal
-    print(t)
-
-    if t.search(6) is not None:
-        print("The value 6 exists")
-    else:
-        print("The value 6 doesn't exist")
-
-    if t.search(-1) is not None:
-        print("The value -1 exists")
-    else:
-        print("The value -1 doesn't exist")
-
-    if not t.empty():
-        print("Max Value: ", t.get_max().value)
-        print("Min Value: ", t.get_min().value)
-
-    for i in testlist:
-        t.remove(i)
-        print(t)
 
 
 if __name__ == "__main__":
     import doctest
 
     doctest.testmod()
-    # binary_search_tree()
diff --git a/data_structures/queue/circular_queue.py b/data_structures/queue/circular_queue.py
index 93a6ef805c7c..e8321c79c6f4 100644
--- a/data_structures/queue/circular_queue.py
+++ b/data_structures/queue/circular_queue.py
@@ -92,3 +92,9 @@ def dequeue(self):
         self.front = (self.front + 1) % self.n
         self.size -= 1
         return temp
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()
diff --git a/data_structures/queue/linked_queue.py b/data_structures/queue/linked_queue.py
index 21970e7df965..74d02fb5500c 100644
--- a/data_structures/queue/linked_queue.py
+++ b/data_structures/queue/linked_queue.py
@@ -149,6 +149,6 @@ def clear(self) -> None:
 
 
 if __name__ == "__main__":
-    from doctest import testmod
+    import doctest
 
-    testmod()
+    doctest.testmod()
diff --git a/data_structures/queue/priority_queue_using_list.py b/data_structures/queue/priority_queue_using_list.py
index c5cf26433fff..3387457356ba 100644
--- a/data_structures/queue/priority_queue_using_list.py
+++ b/data_structures/queue/priority_queue_using_list.py
@@ -59,7 +59,7 @@ class FixedPriorityQueue:
     >>> fpq.dequeue()
     Traceback (most recent call last):
     ...
-    data_structures.queue.priority_queue_using_list.UnderFlowError: All queues are empty
+    priority_queue_using_list.UnderFlowError: All queues are empty
     >>> print(fpq)
     Priority 0: []
     Priority 1: []
@@ -78,6 +78,21 @@ def enqueue(self, priority: int, data: int) -> None:
         Add an element to a queue based on its priority.
         If the priority is invalid ValueError is raised.
         If the queue is full an OverFlowError is raised.
+
+        Examples
+        Those test should fail and raise Overflowerror and value exception.
+
+        >>> fpq = FixedPriorityQueue()
+        >>> fpq.enqueue(3, 10)
+        Traceback (most recent call last):
+        ...
+        ValueError: Valid priorities are 0, 1, and 2
+        >>> fpq = FixedPriorityQueue()
+        >>> q = [fpq.enqueue(0,5) for _ in range(101)]
+        Traceback (most recent call last):
+        ...
+        OverflowError: Maximum queue size is 100
+
         """
         try:
             if len(self.queues[priority]) >= 100:
@@ -141,9 +156,16 @@ class ElementPriorityQueue:
     >>> epq.dequeue()
     Traceback (most recent call last):
         ...
-    data_structures.queue.priority_queue_using_list.UnderFlowError: The queue is empty
+    priority_queue_using_list.UnderFlowError: The queue is empty
     >>> print(epq)
     []
+
+
+    >>> epq2 = ElementPriorityQueue()
+    >>> q = [[epq2.enqueue(11)] for _ in range(101)]
+    Traceback (most recent call last):
+    ...
+    priority_queue_using_list.OverFlowError: Maximum queue size is 100
     """
 
     def __init__(self):
@@ -153,6 +175,7 @@ def enqueue(self, data: int) -> None:
         """
         This function enters the element into the queue
         If the queue is full an Exception is raised saying Over Flow!
+
         """
         if len(self.queue) == 100:
             raise OverFlowError("Maximum queue size is 100")
@@ -177,56 +200,7 @@ def __str__(self) -> str:
         return str(self.queue)
 
 
-def fixed_priority_queue():
-    fpq = FixedPriorityQueue()
-    fpq.enqueue(0, 10)
-    fpq.enqueue(1, 70)
-    fpq.enqueue(0, 100)
-    fpq.enqueue(2, 1)
-    fpq.enqueue(2, 5)
-    fpq.enqueue(1, 7)
-    fpq.enqueue(2, 4)
-    fpq.enqueue(1, 64)
-    fpq.enqueue(0, 128)
-    print(fpq)
-    print(fpq.dequeue())
-    print(fpq.dequeue())
-    print(fpq.dequeue())
-    print(fpq.dequeue())
-    print(fpq.dequeue())
-    print(fpq)
-    print(fpq.dequeue())
-    print(fpq.dequeue())
-    print(fpq.dequeue())
-    print(fpq.dequeue())
-    print(fpq.dequeue())
-
-
-def element_priority_queue():
-    epq = ElementPriorityQueue()
-    epq.enqueue(10)
-    epq.enqueue(70)
-    epq.enqueue(100)
-    epq.enqueue(1)
-    epq.enqueue(5)
-    epq.enqueue(7)
-    epq.enqueue(4)
-    epq.enqueue(64)
-    epq.enqueue(128)
-    print(epq)
-    print(epq.dequeue())
-    print(epq.dequeue())
-    print(epq.dequeue())
-    print(epq.dequeue())
-    print(epq.dequeue())
-    print(epq)
-    print(epq.dequeue())
-    print(epq.dequeue())
-    print(epq.dequeue())
-    print(epq.dequeue())
-    print(epq.dequeue())
-
-
 if __name__ == "__main__":
-    fixed_priority_queue()
-    element_priority_queue()
+    import doctest
+
+    doctest.testmod()
diff --git a/data_structures/queue/queue_on_list.py b/data_structures/queue/queue_on_list.py
index 485cf0b6f7a3..94d0eaf9e6e9 100644
--- a/data_structures/queue/queue_on_list.py
+++ b/data_structures/queue/queue_on_list.py
@@ -50,3 +50,9 @@ def get_front(self):
 
     def size(self):
         return self.length
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()
diff --git a/data_structures/queue/queue_on_pseudo_stack.py b/data_structures/queue/queue_on_pseudo_stack.py
index 7fa2fb2566af..5fa05c5d598b 100644
--- a/data_structures/queue/queue_on_pseudo_stack.py
+++ b/data_structures/queue/queue_on_pseudo_stack.py
@@ -7,6 +7,18 @@ def __init__(self):
         self.length = 0
 
     def __str__(self):
+        """
+        >>> q = Queue()
+        >>> q.put(3)
+        >>> q.put(5)
+        >>> q.put(7)
+        >>> print(q)
+        <3, 5, 7>
+
+        >>> q = Queue()
+        >>> print(q)
+        <>
+        """
         printed = "<" + str(self.stack)[1:-1] + ">"
         return printed
 
@@ -15,6 +27,12 @@ def __str__(self):
         item to enqueue"""
 
     def put(self, item):
+        """
+        >>> q = Queue()
+        >>> q.put(3)
+        >>> assert q.stack == [3]
+        >>> assert q.length == 1
+        """
         self.stack.append(item)
         self.length = self.length + 1
 
@@ -24,6 +42,37 @@ def put(self, item):
         item that was dequeued"""
 
     def get(self):
+        """
+        Testing get() and inner call to rotate()
+
+        >>> q = Queue()
+        >>> q.put(3)
+        >>> q.put(5)
+        >>> q.put(7)
+        >>> n = q.get()
+        >>> assert n == 3
+        >>> assert q.stack == [5,7]
+
+        >>> q2 = Queue()
+        >>> q2.put(3)
+        >>> n = q2.get()
+        >>> n = q2.get()
+        Traceback (most recent call last):
+        ...
+        IndexError: The queue is empty
+
+        >>> q3 = Queue()
+        >>> n = q3.get()
+        Traceback (most recent call last):
+        ...
+        IndexError: The queue is empty
+
+        >>> q4 = Queue()
+        >>> q4.put(3)
+        >>> n = q4.get()
+        >>> assert n == 3
+        """
+
         self.rotate(1)
         dequeued = self.stack[self.length - 1]
         self.stack = self.stack[:-1]
@@ -33,10 +82,22 @@ def get(self):
 
     """Rotates the queue {@code rotation} times
     @param rotation
+    @requirement: |self.length| > 0
         number of times to rotate queue"""
 
     def rotate(self, rotation):
+        """
+        >>> q = Queue()
+        >>> q.put(3)
+        >>> q.put(5)
+        >>> q.put(7)
+        >>> q.rotate(2)
+        >>> assert q.stack == [7,3,5]
+        """
+
         for i in range(rotation):
+            if self.length == 0:
+                raise IndexError("The queue is empty")
             temp = self.stack[0]
             self.stack = self.stack[1:]
             self.put(temp)
@@ -46,6 +107,18 @@ def rotate(self, rotation):
     @return item at front of self.stack"""
 
     def front(self):
+        """
+        >>> q = Queue()
+        >>> q.put(3)
+        >>> n = q.front()
+        >>> assert n == 3
+
+        >>> q2 = Queue()
+        >>> n = q2.front()
+        Traceback (most recent call last):
+        ...
+        IndexError: The queue is empty
+        """
         front = self.get()
         self.put(front)
         self.rotate(self.length - 1)
@@ -54,4 +127,15 @@ def front(self):
     """Returns the length of this.stack"""
 
     def size(self):
+        """
+        >>> q = Queue()
+        >>> q.size()
+        0
+        """
         return self.length
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()