Dependency injection with unique_ptr to mock

Question

I have a class Foo that uses class Bar. Bar is used only in Foo and Foo is managing Bar, therefore I use unique_ptr (not a reference, because I don\'t need Bar outside of Fo

Answer 1

You can keep a reference to the mocked object before passing it to the constructor. I think it makes the code a tad bit brittle, due to member initialization ordering, but it is clearer semantically what it means. Ownership of BarMock still belongs solely to Foo, with a reference handle kept by FooTest (similar to this answer).

Basically the same as your answer, but using reference instead of a raw pointer

class FooTest : public ::testing::Test
{
    protected:
        FooTest() :
            bar_mock_ptr(std::make_unique()),
            bar_mock(*bar_mock_ptr),
            foo(std::move(bar_mock_ptr))
        {}
    private:
        // This must be declared before bar_mock due to how member initialization is ordered
        std::unique_ptr bar_mock_ptr; // moved and should not be used anymore
    protected:
        BarMock& bar_mock;
        Foo foo; //ensure foo has the same lifetime as bar_mock
}