diff --git a/.gitignore b/.gitignore
index 9ef9604..67f0073 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 build
+.cache
 
diff --git a/include/shapes/Rectangle.hpp b/include/shapes/Rectangle.hpp
index 64434bd..c6ef150 100644
--- a/include/shapes/Rectangle.hpp
+++ b/include/shapes/Rectangle.hpp
@@ -1,12 +1,15 @@
+#ifndef RECTANGLE
+#define RECTANGLE
+
 #include "Shape.hpp"
 
-struct Rectangle : public Shape
-{
+struct Rectangle : public Shape {
   Rectangle(const double sideLen);
 
-  double area() override;
+  double area() const override;
 
 private:
   double sideLen{};
 };
 
+#endif
diff --git a/include/shapes/Shape.hpp b/include/shapes/Shape.hpp
index dfb94f9..ceb9562 100644
--- a/include/shapes/Shape.hpp
+++ b/include/shapes/Shape.hpp
@@ -1,11 +1,14 @@
+#ifndef SHAPE
+#define SHAPE
+
 #include <cstdint>
 #include <iostream>
 
 struct Shape
 {
-  virtual double area() = 0;
+  virtual double area() const = 0;
 
-  double getArea();
+  double getArea() const;
 
 protected:
   Shape() = delete;
@@ -13,3 +16,5 @@ protected:
 
   size_t numSides{};
 };
+
+#endif
diff --git a/include/shapes/Triangle.hpp b/include/shapes/Triangle.hpp
index 79a1dd2..ed4984a 100644
--- a/include/shapes/Triangle.hpp
+++ b/include/shapes/Triangle.hpp
@@ -1,11 +1,16 @@
+#ifndef TRIANGLE
+#define TRIANGLE
+
 #include "Shape.hpp"
 
 struct Triangle : public Shape
 {
   Triangle(const double sideLen);
 
-  double area() override;
+  double area() const override;
 
 private:
   double sideLen{};
 };
+
+#endif
diff --git a/src/shapes/Rectangle.cpp b/src/shapes/Rectangle.cpp
index a126755..26fba35 100644
--- a/src/shapes/Rectangle.cpp
+++ b/src/shapes/Rectangle.cpp
@@ -1,5 +1,5 @@
 #include "Rectangle.hpp"
 
-Rectangle::Rectangle(const double sideLen) : sideLen(sideLen) {}
+Rectangle::Rectangle(const double sideLen) : Shape(sideLen) {}
 
-Rectangle::area() { return sideLen * sideLen; }
+double Rectangle::area() const { return sideLen * sideLen; }
diff --git a/src/shapes/Shape.cpp b/src/shapes/Shape.cpp
index faa7096..b87dbed 100644
--- a/src/shapes/Shape.cpp
+++ b/src/shapes/Shape.cpp
@@ -5,4 +5,4 @@ Shape::Shape(const size_t numSides) : numSides(numSides)
 
 }
 
-double Shape::getArea(){ return area(); }
+double Shape::getArea() const{ return area(); }
diff --git a/src/shapes/Triangle.cpp b/src/shapes/Triangle.cpp
index 13087af..66d3353 100644
--- a/src/shapes/Triangle.cpp
+++ b/src/shapes/Triangle.cpp
@@ -1,5 +1,5 @@
 #include "Triangle.hpp"
 
-Triangle::Triangle(const double sideLen) : sideLen(sideLen) {}
+Triangle::Triangle(const double sideLen) : Shape::Shape(sideLen) {  }
 
-Triangle::area() { return 0.5 * sideLen * sideLen; }
+double Triangle::area() const { return 0.5 * sideLen * sideLen; }
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 4cbf914..f28530e 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -2,8 +2,6 @@ add_executable(unittest
   ${CMAKE_CURRENT_LIST_DIR}/TestShape.cpp
 )
 
-message("${CMAKE_CURRENT_LIST_DIR}/TestShape.cpp")
-
 target_link_libraries(unittest PUBLIC
   Shapes
   gtest_main
diff --git a/test/TestShape.cpp b/test/TestShape.cpp
index 3801d5b..f89ada6 100644
--- a/test/TestShape.cpp
+++ b/test/TestShape.cpp
@@ -1,4 +1,4 @@
-#include <gtest/gtest.hpp>
+#include <gtest/gtest.h>
 
 #include "Rectangle.hpp"
 #include "Triangle.hpp"