CODEWITHSUNDEEP
c++googletest
Supervisor
Supervisor

Reputation: 602

GTest Typed Test - Using

I want to use 'MyType' from the base class in the 'DoesBlah' test below.

#include <gtest/gtest.h>

template <typename T>
struct MemberVariable
{
    T m_t;
};

struct Base : public ::testing::Test
{
    template <typename MemberType>
    using MyType = MemberVariable<MemberType>;
};

template <typename DerivedType>
struct Derived : public Base
{
};

typedef ::testing::Types<int, char> MyTypes;
TYPED_TEST_CASE(Derived, MyTypes);

TYPED_TEST(Derived, DoesBlah)
{
    MyType<TypeParam> test;
    test.m_t = (TypeParam)1;
    ASSERT_EQ(test.m_t, 1);
}

However, I get the following compilation error:

gti/specific/level/Test.t.cpp: In member function 'virtual void Derived_DoesBlah_Test<gtest_TypeParam_>::TestBody()':
gti/specific/level/Test.t.cpp:25:5: error: 'MyType' was not declared in this scope
     MyType<TypeParam> test;

I tried using TestFixture::MyType, typename TestFixture::MyType, but both did not work.

How can I get Derived to recognize that there's something called 'MyType'?

Upvotes: 2

Views: 6638

Answers (1)

aschepler
aschepler

Reputation: 72271

With some simplifications, the macro TYPED_TEST(Derived, DoesBlah) expands to something like:

template <typename TypeParam>
class Derived_DoesBlah_Test : public Derived<TypeParam>
{
private:
    typedef Derived<TypeParam> TestFixture;
    virtual void TestBody();
};
template <typename TypeParam>
void Derived_DoesBlah_Test<TypeParam>::TestBody()

So the {} block that follows is the function definition for a member of a template class which derives from Derived<TypeParam>. The typedef for TestFixture is available, but it depends on the template parameter TypeParam, so it is considered a dependent type. What's more, you want to access a template member of that dependent type. So you need both the typename and template keywords:

{
    typename TestFixture::template MyType<TypeParam> test;
    test.m_t = (TypeParam)1;
    ASSERT_EQ(test.m_t, 1);
}

For more about dependent types and using the typename and template keywords in declarations and expressions, see this SO question.

Upvotes: 4

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