Refactor C++ version of the Gilded Rose kata

* Make it possible to build and run tests in CLion
  and Visual Studio 2019 out of the box

* Provide four types of initial test using different test frameworks:
  * Catch2 test framework
    * Traditional unit testing using Catch2
    * Approval test using Catch2
  * Google Test test framework
    * Traditional unit testing using Google Test
    * Approval test using Google Test

* The different types of initial test are located in separate folders
  in the test folder.

* Remove scripts to build and run tests and replace
  with instructions in the cpp README.md

* Use C++17

* Use CMake => 3.13

cpp/README.md

@@ -1,38 +1,68 @@
-TL;DR;
--------
-run-once.sh runs your tests once
+# C++ version of Gilded Rose refactoring kata
 
-Before this will work you will need:
-  - make and a C++ compiler (like gcc) is installed on your system and is in the PATH
-  - The GTest framework in the directory gtest.
-  - If your IDE does the compilation and linking, you should remove the first 3 lines
-    in the run-once.sh file.
+## Introduction
+The C++ version of the Gilded Rose refactoring kata is available in four variants using different test frameworks:
 
-More Verbose Instructions
--------------------------
+* Catch2 test framework
+  1. Traditional unit test with the [Catch2](https://github.com/catchorg/Catch2) test framework in the `test/cpp_catch2_unittest` folder.
+  2. [Approval tests](https://github.com/approvals/ApprovalTests.cpp) with the [Catch2](https://github.com/catchorg/Catch2) test framework in the `test/cpp_catch2_approvaltest` folder.
+* Google Test framework
+  1. Traditional unit test with the [Googletest](https://github.com/google/googletest) test framework in the `test/cpp_googletest_unittest` folder.
+  2. [Approval tests](https://github.com/approvals/ApprovalTests.cpp) with the [Googletest](https://github.com/google/googletest) test framework in the `test/cpp_googletest_approvaltest` folder.
 
-Create a clone of both GildedRose-Refactoring-Kata and googletest in a directory we'll call ${ROOT_INSTALL_DIR}:
+The `GildedRose.cc` file, i.e. the code under test, is identical in all four variants.
 
-    cd ${ROOT_INSTALL_DIR}
-    git clone https://github.com/emilybache/GildedRose-Refactoring-Kata
-    git clone https://github.com/google/googletest
+## Prerequisites
 
-Make googletest by running make in subfolder googletest/googletest/make:
+* CMake version >= 3.13
+* C++ compiler that support C++17
 
-    cd googletest/googletest/make
-    make
+## How to build and run tests in a terminal
 
-Create a softlink in the GildedRose-Refactoring-Kata clone pointing at the googletest code:
+### Build tests
 
-    cd ${ROOT_INSTALL_DIR}/GildedRose-Refactoring-Kata/cpp
-    ln -s ${ROOT_INSTALL_DIR}/googletest/googletest gtest
+    $ cd ${GIT_FOLDER}/GildedRose-Refactoring-Kata/cpp
+    $ mkdir build
+    $ cd build
+    $ cmake ..
+    $ cmake --build .
 
-Make the GildedRose-Refactoring-Kata:
+### Show available tests
 
-    make
+    $ cd ${GIT_FOLDER}/GildedRose-Refactoring-Kata/cpp/build
+    $ ctest -N
+    Test project ${GIT_FOLDER}/GildedRose-Refactoring-Kata/cpp/build
+      Test #1: GildedRoseCatch2ApprovalTests
+      Test #2: GildedRoseCatch2UnitTests
+      Test #3: GildedRoseGoogletestApprovalTests
+      Test #4: GildedRoseGoogletestUnitTests
 
-Then you should be able to run the tests:
+### Run all tests
 
-    ./run_once.sh
+    $ ctest
 
-If you have been successful, then you should see a failing test, "GildedRoseTest.Foo".
+### Run all tests with verbose output
+
+    $ ctest -VV
+
+### Run a specific test with verbose output
+
+    $ ctest -VV --tests-regex Catch2Approval
+
+## How to build and run tests using the [CLion IDE](https://www.jetbrains.com/clion/)
+
+1. Start CLion
+2. Select menu `File - Open...`
+3. Select folder `${GIT_FOLDER}/GildedRose-Refactoring-Kata/cpp`
+4. Select menu `Build - Build Project`
+4. Select menu `Run - Run...`
+4. Select what test variant to run, e.g. `GildedRoseCatch2ApprovalTests`.
+
+## How to build and run tests using Visual Studio 2019 
+
+1. Start Visual Studio 2019
+2. Select `Open a local folder`
+3. Select folder `${GIT_FOLDER}/GildedRose-Refactoring-Kata/cpp`
+4. Wait for message `CMake generation finished.` in the CMake output window at the bottom
+5. Select what test variant to run in the drop down menu for Startup Items, e.g. `GildedRoseCatch2ApprovalTests.exe`.
+6. Select menu `Debug - Start`