Obscure error when parametrized gtest with std::pairs fails

Question

When using a parametrized test in gtest where the parameters are std::pair, when the test fails, the output is like

[  FAILED  ] 1 test, listed below:
[  FAILED  ] MyTest/MyFixtureTest.MyTest/1, where GetParam() =  (4-byte object <00-00 00-00>, 4-byte object <01-00 00-00>) 

How to pretty print the error, for example in case of enums showing the int or the enum value?

The test is something like this

enum class A
{
  A=0,
  B,
  C
};

enum class B
{
  A=0,
  B,
  C
};

B convertAtoB(A a)
{
  if (a==A::A)
  {
    return B::A;
  }
  else if (a==A::B)
  {
    return B::B;
  }
  else
  {
    return B::C;
  }
}

class MyFixtureTest :
  public ::testing::TestWithParam<std::pair<A, B>>
{ 
};

TEST_P(MyFixtureTest, MyTest) {
  A a = GetParam().first;
  EXPECT_EQ(convertAtoB(a), GetParam().second);
  
}

INSTANTIATE_TEST_CASE_P(
        MyTestP,
        MyFixtureTest,
        ::testing::Values(
                std::make_pair(A::A, B::B),
                std::make_pair(A::B, B::B),
                std::make_pair(A::C, B::C)
  )
);

Answer 1

Use the same technique as in Teaching GoogleTest How to Print Your Values. E.g. define PrintTo:

void PrintTo(const std::pair<A, B>& p, std::ostream* os) {
    *os << "(" << (int)p.first << "," << (int)p.second << ")";
}

You can also define operator<< for your enums to avoid casting to int.

As a side note, googletest knows how to print std::pair, it just didn't know how to print your custom types.