[gtest] First commit of gtest, and first UT for SaveStorageValue() function

* Include README.md with some basic information about preparing the setup
* UT for SaveStorageValue() function

gtest/README.md

@@ -0,0 +1,66 @@
+## Unit test for raylib using Google Test
+
+We are going to use the Open source Tool Google Test for generating and launching  Unit Tests. Please consider reading some information before start:
+
+* https://en.wikipedia.org/wiki/Unit_testing
+* https://github.com/google/googletest
+* https://github.com/google/googletest/blob/master/googletest/docs/primer.md
+
+
+
+## Steps for preparing the Google Test environment for Raylib
+
+1) Intall **MinGW** if it's not already installed.
+
+2) Install **Cmake** from: https://cmake.org/download/
+
+3)  Clone **Google Test** repository  https://github.com/google/googletest
+
+The expected download directory  for google test is:
+
+	`C:\GitHub\googletest`
+If a different one is choosen, please update the path in the bat file.
+
+4) Create a directory for the build:
+
+	`C:\GitHub\googletest\mybuild`
+
+5) Configure and generate with CMake, as describe in image
+
+	![Cmake configuration](docs\configure_and_generate_with_cmake.png "Cmake configuration")
+
+6)  Compile google test, using **make**:
+	`C:\GitHub\googletest\mybuild>mingw32-make`
+
+
+
+
+## Compile and run unit test ##
+
+The raylib library contains a folder called gtest with the implemented Unit Test, and a batch file for its compilation and execution. 
+
+**IMPORTANT**:
+* The batch file contains the absolute paths to the Google test static library compiled in the previous steps. If the paths are different, please update them.
+
+* As we are going to test **raylib** and its included in the compilation via `-lraylib` sure that MINGGW contains your last compilation of raylib, so you are testing the latest changes in raylib. Copy libraylib.a from `raylib\src` to `C:\MinGW\i686-w64-mingw32\lib`
+
+* The compilation of the Unit Test has not the option `-mwindows` so al the **TRACELOG** from raylib will be seen on the console.
+
+For compiling and test execution run the bach file for one unit test file:
+
+`C:\GitHub\raylib\gtest>raylib_compile_gtest.bat core_ut.cpp`
+
+
+The result shall looks something like this:
+
+	![Example execution gtest](docs\example_execution_gtest.png "Example execution gtest")
+
+
+
+
+
+
+
+
+
+

gtest/core_ut.cpp

@@ -0,0 +1,81 @@
+#include "gtest/gtest.h"
+#include "raylib.h" 
+
+// We expect storing and loading OK in position 0
+TEST(SaveStorageValue, test_basic_save_load) {
+	int in=19;
+	int out=0;
+	int position=0;
+
+	SaveStorageValue(position,in);
+	out=LoadStorageValue(position);
+    
+    EXPECT_EQ (in,out);
+    
+}
+
+
+// We expect to create file storage.data and save/load OK
+TEST(SaveStorageValue, create_storage_data_file) {
+	int in=19;
+	int out=0;
+	int position=0;
+
+	system("del storage.data");
+	SaveStorageValue(position,in);
+	out=LoadStorageValue(position);
+    EXPECT_EQ (in,out);
+}
+
+
+// We expect to create and increase the size of the file storage.data save/load OK
+TEST(SaveStorageValue, increase_storage_data_file) {
+	int in=19;
+	int out=0;
+	int position=0;
+
+	system("del storage.data");
+	SaveStorageValue(position,in);
+	out=LoadStorageValue(position);
+    EXPECT_EQ (in,out);
+	
+	position=23;
+	SaveStorageValue(position,in);
+	out=LoadStorageValue(position);
+    EXPECT_EQ (in,out);
+  
+}
+
+
+ // We expect failure in SaveStorageValue, and so save is not performed. Load gives different data than save
+TEST(SaveStorageValue, test_negative_position) {
+	int in=19;
+	int out=0;
+	int position=-1;
+	SaveStorageValue(position,in);
+	out=LoadStorageValue(position);
+    
+    EXPECT_NE (in,out);
+    
+}
+
+
+
+  // We expect a failure in SaveStorageValue, and so save is not performed. Load gives different data than save
+TEST(SaveStorageValue, fail_realloc_in_SaveStorageValue) {
+	int in=19;
+	int out=0;
+	int position=INT_MAX;
+	
+	SaveStorageValue(position,in);
+	out=LoadStorageValue(position);
+    
+    EXPECT_NE (in,out);
+    
+}
+
+
+int main(int argc, char **argv) {
+    ::testing::InitGoogleTest(&argc, argv);
+    return RUN_ALL_TESTS();
+}

gtest/raylib_compile_gtest.bat

@@ -0,0 +1,40 @@
+::@echo off
+:: .
+:: Compile your test using :  raylib_compile_gtest.bat core_ut.cpp
+:: .
+:: > Setup required Environment
+:: -------------------------------------
+set GTEST_INCLUDE_DIR=C:\GitHub\googletest\googletest\include\
+set GTEST_LIB=C:\GitHub\googletest\mybuild\lib\libgtest.a
+set GTEST_LIB_MAIN=C:\GitHub\googletest\mybuild\lib\libgtest_main.a
+
+:: Get full filename path for input file %1
+set FILENAME=%~f1
+set NAMEPART=%FILENAME:~0,-4%
+cd %~dp0
+:: .
+:: > Cleaning latest build
+:: ---------------------------
+cmd /c if exist %NAMEPART%.exe del /F %NAMEPART%.exe
+
+:: > Compiling program
+:: --------------------------
+
+g++  -c %NAMEPART%.cpp -I%GTEST_INCLUDE_DIR%
+
+:: .
+:: > Linking program
+:: --------------------------
+:: -s        : Remove all symbol table and relocation information from the executable
+:: -O2       : Optimization Level 2, this option increases both compilation time and the performance of the generated code
+:: -std=c99  : Use C99 language standard
+:: -Wall     : Enable all compilation Warnings
+
+g++ -pthread -o %NAMEPART%.exe %NAMEPART%.o %GTEST_LIB% %GTEST_LIB_MAIN% -lraylib -lopengl32 -lgdi32 -lwinmm -std=c99 -Wall 
+:: .
+:: > Executing program
+:: -------------------------
+cmd /c if exist %NAMEPART%.exe %NAMEPART%.exe
+
+
+