Non-instantiable Google test fixture super-class

Question

I wish to define a super-class which is non-instantiable for my Google test fixtures. The super-class will initialise the members and have some default tests. The sub-classes will extend the super-class, and have specific tests.

The following is the base class:

class BaseTest : public ::testing::Test
{
protected:
    BaseTest(...) {} // constructor with args to setup members

    void SetUp() {} // sets up the internals
};

TEST_F(BaseTest, ACommonTest) {} // common test case

The derived class:

class DerivedTest : public BaseTest
public:
    DerivedTest() : BaseTest(...) {} // default no args constructor

    void SetUp() { BaseTest::SetUp(); }
};

TEST_F(DerivedTest, ASpecificTest) {} // specific test case

What I want is the test to not instantiate the BaseTest, instead to instantiate the DerivedTest and invoke both methods, ACommonTest and ASpecificTest.

What it is actually doing at this time, is instantiating the BaseTest and running ACommonTest on it. Then instantiating the DerivedTest and running the ASpecificTest.

Answer 1

You can probably make use of "Typed Tests" or "Type-Parameterized Tests" here.

So for example, if you remove TEST_F(BaseTest, ACommonTest) {} (since that's where you instantiate a BaseTest rather than one derived from it), you can replace it with:

template <typename T>
class DerivedCommonTest : public BaseTest {
public:
    DerivedCommonTest() : BaseTest() {}
    virtual void SetUp() { BaseTest::SetUp(); }
};

typedef ::testing::Types<Foo, Bar> MyTypes;
TYPED_TEST_CASE(DerivedCommonTest, MyTypes);

TYPED_TEST(DerivedCommonTest, ACommonTest) {} // common test case

If you really wish to make BaseTest non-instantiable, you could add a pure virtual function to it, and then implement it for each derived type:

class BaseTest : public ::testing::Test {
protected:
    BaseTest() {} // constructor with args to setup members
    virtual void SetUp() {} // sets up the internals
    virtual void PureVirtual() = 0;
};

...

template <typename T>
class DerivedCommonTest : public BaseTest {
public:
    DerivedCommonTest() : BaseTest() {}
    virtual void SetUp() { BaseTest::SetUp(); }
    virtual void PureVirtual() {}
};

...    

class DerivedTest : public BaseTest {
public:
    DerivedTest() : BaseTest(...) {} // default no args constructor
    virtual void SetUp() { BaseTest::SetUp(); }
    virtual void PureVirtual() {}
};