how can i test void method using google test framework

Question

example: I have a void method which just prints the elements of an array.

#include <stdio.h>

void PrintNumbers();

int arr[10];

int main(){

        int i;
        int value = 0;

        for(i = 0 ; i<10; i++)
                arr[i] = value++;

         PrintNumbers();

        return 0;
}

PrintNumbers(){

        int i;

        for(i = 0 ; i < 10 ; i++)
                cout <<"arr["<< arr[i] << "]" << endl;
}

Answer 1

To have the method tested properly in this case, I'd inject the stream to the method:

void PrintNumbers(std::ostream& os = std::cout) {
    int a = 42;
    os << "Expected " << a;
}

TEST(PrintNumbersTest, TestWithStringStream) {
    std::stringstream myStream;
    PrintNumbers(myStream);

    ASSERT_EQ("Expected 42", myStream.str());
}

Dependency injection is one of the options here and is widely acceptable. Because of the default argument, the caller doesn't have to change anything.