Testing the contents in std::unordered_map without worrying about the order

Question

I am looking to check whether the strings outputted match against the expected one without worrying about the order in which they are printed.

Here, std::unordered_map stores the A objects as values and since it's not ordered, it becomes tricky since the output can be either foo\nbar\n or bar\nfoo\n.

Any ways it could be tested in google mock?

class A
{
    std::string _name;

    public:
    A(std::string name) : _name(name) {}
    void foo() 
    {
        std::cout << _name << "\n";
    }
};

TEST(UnorderedMatch, A) 
{
    A a1{"foo"};
    A a2{"bar"};
    std::string expectedOut = "foo\nbar\n"; 
    std::unordered_map<int, A> m1 = { {1, a1}, {2, a2} };

    // test: foo()'s output matches expectedOut
    // verify output is "foo\nbar\n" without worrying about its order 
    for (auto e : m1)
    {
        e.second.foo();
    }
}

Answer 1

Assuming that by verification you mean using gmock instruments, you could employ UnorderedElementsAre mentioned here. Otherwise refer to advice given in the comments.

Please note that using UnorderedElementsAre requires a comparison operator in A, so I've changed its definition a bit:

class A
{
    std::string _name;

public:
    auto operator<=>(A const&) const = default; // required by test
    A(std::string name) : _name(name) {}
    // ...
};

Example of UnorderedElementsAre usage:

TEST(UnorderedMatch, A)
{
    A a1{"foo"};
    A a2{"bar"};

    std::unordered_map<int, A> m1 = { {1, a1}, {2, a2}, };

    using namespace ::testing;
    using std::string_literals::operator""s;

    EXPECT_THAT(m1, UnorderedElementsAre( Pair(_, "bar"s), Pair(_, "foo"s) ));
}