Computing unit tests in QT creator - multiple definitions of core

I would like to use the Catch unit test framework to test my projects. I read a tutorial on how to write tests, it was pretty simple. I tried to create a really simple project in QT builder that includes these files:

main.cpp
tests.cpp
factorial.cpp
factorial.h
catch.hpp

      

        
        
        
      

    

main.cpp:

#include <stdio.h>
#include "factorial.h"

int main(void)
{
    printf("%d", factorial(5));
    return 0;
}

      

        
        
        
      

    

tests.cpp:

#define CATCH_CONFIG_MAIN
#include "catch.hpp"
#include "factorial.h"

TEST_CASE( "factorial on valid numbers", "[factorial]" ) {
    REQUIRE( factorial(1) == 1 );
    REQUIRE( factorial(5) == 120 );
    REQUIRE( factorial(10) == 3628800 );
}

      

        
        
        
      

    

factorial.cpp:

#include "factorial.h"

int factorial(int number)
{
    if(number < 0)
        return -1;
    int result = 1;
    for(int i = number; i > 0; i--)
        result *= i;
    return result;
}

      

        
        
        
      

    

factorial.h:

#ifndef FACTORIAL
#define FACTORIAL

int factorial(int number);

#endif // FACTORIAL

      

        
        
        
      

    

and catch.hpp is the catch scheme for unit tests

I am coding in C, not C ++, the ".cpp" extension only happens because of the catch which does not work with files with the ".c" extension

There is another file called testing.pro containing

Q

MAKE_CFLAGS += -std=c99 -pedantic -Wall -Wextra
TEMPLATE = app
CONFIG += console
CONFIG -= app_bundle
CONFIG -= qt

SOURCES += \
    main.cpp \
    factorial.cpp \
    tests.cpp

include(deployment.pri)
qtcAddDeployment()

HEADERS += \
    catch.hpp \
    factorial.h

      

        
        
        
      

    

This file was created by the creator of QT.

Ok, and my problem is that when I try to build this project, I get the error: "multiple definition of main".

I understand. I have a main file called main.cpp and also in tests.cpp. But I don't know what to do to make it work. I want to have a project with a fully working main and test file where I can test my functions. I have searched almost everywhere. I guess I need to somehow organize my project in the QT creator, but I have no idea how to do this. I have no idea how this is supposed to work.

Thanks for the advice