added more tests

Project 5/Stack.py

@@ -19,7 +19,9 @@ class Stack[T]:
 
     def __init__(self):
        
-        pass
+        ''' initializes an empty stack '''
+        self._data = LinkedList()
+
     def __len__(self) -> int:
         ''' allows the len function to be called using an ArrayStack object, e.g.,
                stack = ArrayStack()
@@ -27,7 +29,7 @@ class Stack[T]:
         Returns:
             number of elements in the stack, as an integer
         '''
-        pass
+        return len(self._data)
 
     def push(self, item: T) -> None: 
         ''' pushes a given item of arbitrary type onto the stack
@@ -36,7 +38,7 @@ class Stack[T]:
         Returns:
             None
         '''
-        pass
+        self._data.insert_head(item)
 
     def pop(self) -> T:
         ''' removes the topmost element from the stack and returns that element
@@ -45,7 +47,9 @@ class Stack[T]:
         Raises:
             EmptyError exception if the stack is empty
         '''
-        pass
+        if self.is_empty():
+            raise EmptyError("Stack is empty")
+        return self._data.remove_head()
 
     def peek(self) -> T:
         ''' returns the topmost element from the stack without modifying the stack
@@ -54,14 +58,16 @@ class Stack[T]:
         Raises:
             EmptyError exception if the stack is empty
         '''
-        pass
+        if self.is_empty():
+            raise EmptyError("Stack is empty")
+        return self._data.get_head()
 
     def is_empty(self) -> bool:
         ''' indicates whether the stack is empty
         Returns:
             True if the stack is empty, False otherwise
         '''
-        pass
+        return len(self._data) == 0
 
     def __str__(self) -> str:
         ''' returns an str implementation of the Stack '''
@@ -69,9 +75,40 @@ class Stack[T]:
         return str(self._data)
 
 def main():
-    # add your tests here!
+    '''test functions'''
+    s = Stack() # I added this so stack doesnt need to be reinitialized for each test
+
+    assert len(s) == 0
+    assert s.is_empty() is True
+
+    s.push(10)
+    assert len(s) == 1
+    assert s.peek() == 10
+
+    s.push(20)
+    s.push(30)
+    assert len(s) == 3
+    assert s.peek() == 30
+
+    assert s.pop() == 30
+    assert s.pop() == 20
+    assert s.pop() == 10
+    assert s.is_empty() is True
+
+    try:
+        s.pop()
+        assert False
+    except EmptyError:
         pass
 
+    try:
+        s.peek()
+        assert False
+    except EmptyError:
+        pass
+
+    print("All Stack tests passed.") #only runs if all previous tests pass
+
 if __name__ == "__main__":
     main()