diff --git a/Assignment_3/lib/ADT_Stack.cpp b/Assignment_3/lib/ADT_Stack.cpp
index 1e0e258..7e1c042 100644
--- a/Assignment_3/lib/ADT_Stack.cpp
+++ b/Assignment_3/lib/ADT_Stack.cpp
@@ -1,5 +1,67 @@
-class Stack {
-    void push(int element, bool output);
-    void pop(int element, bool output);
-    void size(int element, bool output);
-};
\ No newline at end of file
+#include <stack>
+#include<stdexcept>
+#include <sstream>
+#include <stdlib.h>
+
+#include "ADT_Stack.h"
+
+operation create_operation(methodname name, int value) {
+    operation op;
+    op.method = name;
+    op.value = value;
+    return op;
+}
+
+
+void ADTStack::push(int element){
+    stack.push(element);
+}
+
+void ADTStack::pop(int output) {
+    if (stack.empty() == false) {
+        int top = stack.top();
+        if (output == top){
+            stack.pop();
+        } else {
+            std::ostringstream oss;
+            oss << "Invalid operation: pop " << output << " (actual top: " << top << ")";
+            throw std::invalid_argument(oss.str());
+        }
+    } else {
+        std::ostringstream oss;
+        oss << "Invalid operation: pop " << output << " (stack is empty)";
+        throw std::invalid_argument(oss.str()); 
+    }
+}
+
+void ADTStack::size(int output){
+    int size = stack.size();
+    if (output != size) {
+        std::ostringstream oss;
+        oss << "Invalid operation: size " << output << " (actual size: " << size << ")";
+        throw std::invalid_argument(oss.str());
+    }
+}
+
+void ADTStack::do_op(operation * op) {
+    switch (op->method) {
+        case methodname::push:
+            push(op->value);
+            break;
+        case methodname::pop:
+            pop(op->value);
+            break;
+        case methodname::size:
+            size(op->value);
+            break;
+        default:
+            break;
+    }
+}
+
+void ADTStack::do_ops(std::vector<operation> ops) {
+    for (operation op : ops) {
+        do_op(&op);
+    }
+}
+
diff --git a/Assignment_3/lib/ADT_Stack.h b/Assignment_3/lib/ADT_Stack.h
new file mode 100644
index 0000000..9a6a64a
--- /dev/null
+++ b/Assignment_3/lib/ADT_Stack.h
@@ -0,0 +1,21 @@
+#include <stack>
+#include <vector>
+
+enum methodname {push, pop, size, noop};
+typedef struct _operation{
+  methodname method;
+  int value;
+} operation;
+
+operation create_operation(methodname name, int value);
+
+class ADTStack {
+    private:
+        std::stack<int> stack;
+    public:
+        void push(int element);
+        void pop(int output);
+        void size(int output);
+        void do_op(operation * op);
+        void do_ops(std::vector<operation> ops);
+};
\ No newline at end of file
diff --git a/Assignment_3/lib/CMakeLists.txt b/Assignment_3/lib/CMakeLists.txt
index be8e6f8..12db947 100644
--- a/Assignment_3/lib/CMakeLists.txt
+++ b/Assignment_3/lib/CMakeLists.txt
@@ -1 +1 @@
-add_library(sets STATIC Node.h Node.cpp Stack.h Stack.cpp ADT_Stack.cpp )
+add_library(sets STATIC ADT_Stack.h ADT_Stack.cpp Node.h Node.cpp Stack.h Stack.cpp )
diff --git a/Assignment_3/test/ADT_Stack_test.cpp b/Assignment_3/test/ADT_Stack_test.cpp
new file mode 100644
index 0000000..04a2fba
--- /dev/null
+++ b/Assignment_3/test/ADT_Stack_test.cpp
@@ -0,0 +1,78 @@
+#include <gtest/gtest.h>
+
+#include <vector>
+#include <stdexcept>
+#include <lib/ADT_Stack.h>
+
+TEST(ADTStackTest, SimplePushPop) {
+    std::vector<operation> ops;
+
+    ops.push_back(create_operation(methodname::push, 1));
+    ops.push_back(create_operation(methodname::pop, 1));
+
+    ADTStack * adt = new ADTStack();
+    adt->do_ops(ops);
+}
+
+TEST(ADTStackTest, SimplePopWrong) {
+    std::vector<operation> ops;
+    ops.push_back(create_operation(methodname::push, 2));
+    ops.push_back(create_operation(methodname::pop, 1));
+
+    ADTStack * adt = new ADTStack();
+
+    try {
+        adt->do_ops(ops);
+        FAIL() << "Expected std::invalid_argument";
+    }
+    catch(std::invalid_argument const & err) {
+        EXPECT_EQ(err.what(),std::string("Invalid operation: pop 1 (actual top: 2)"));
+    }
+    catch(...) {
+        FAIL() << "Expected std::invalid_argument";
+    }
+}
+
+TEST(ADTStackTest, PopEmpty) {
+    std::vector<operation> ops;
+    ops.push_back(create_operation(methodname::pop, 1));
+
+    ADTStack * adt = new ADTStack();
+
+    try {
+        adt->do_ops(ops);
+        FAIL() << "Expected std::invalid_argument";
+    }
+    catch(std::invalid_argument const & err) {
+        EXPECT_EQ(err.what(),std::string("Invalid operation: pop 1 (stack is empty)"));
+    }
+    catch(...) {
+        FAIL() << "Expected std::invalid_argument";
+    }
+}
+
+TEST(ADTStackTest, SizeEmpty) {
+    std::vector<operation> ops;
+    ops.push_back(create_operation(methodname::size, 0));
+
+    ADTStack * adt = new ADTStack();
+    adt->do_ops(ops);
+}
+TEST(ADTStackTest, SizeEmptyWrong) {
+    std::vector<operation> ops;
+    ops.push_back(create_operation(methodname::size, 1));
+
+    ADTStack * adt = new ADTStack();
+
+    try {
+        adt->do_ops(ops);
+        FAIL() << "Expected std::invalid_argument";
+    }
+    catch(std::invalid_argument const & err) {
+        EXPECT_EQ(err.what(),std::string("Invalid operation: size 1 (actual size: 0)"));
+    }
+    catch(...) {
+        FAIL() << "Expected std::invalid_argument";
+    }
+}
+
diff --git a/Assignment_3/test/CMakeLists.txt b/Assignment_3/test/CMakeLists.txt
index 133ce92..d2bc02f 100644
--- a/Assignment_3/test/CMakeLists.txt
+++ b/Assignment_3/test/CMakeLists.txt
@@ -10,3 +10,8 @@ add_executable(node_unit_test Node_test.cpp)
 target_link_libraries(node_unit_test PUBLIC gtest gtest_main)
 target_link_libraries(node_unit_test PUBLIC sets)
 add_test(NodeTest node_unit_test)
+
+add_executable(adt_unit_test ADT_Stack_test.cpp)
+target_link_libraries(adt_unit_test PUBLIC gtest gtest_main)
+target_link_libraries(adt_unit_test PUBLIC sets)
+add_test(ADTTest adt_unit_test)