gcovr: cannot analyse class under test in some cases

Question

my intention is to execute code coverage report with gcovr to my tests that are written with gtest framework with CMake.

ClassUnderTest.h:

class ClassUnderTest
{
public:
           uint8_t Start(int in_a, int in_b);

    static uint8_t MethodToTest(int a, const uint8_t *b, uint32_t c);
}

I have 2 test cases. One uses "TEST"s the other uses "TEST_F"s (a.k.a Test fixtures).

Test without Fixture:

TestCase1.cpp:

TEST (Test_Start, MethodToTest_test)
{
    ClassUnderTest       TestObj;

    EXPECT_EQ(TestObj.Start(1,2),0xFF));
}

Test with Fixture:

TestCase2.cpp:
class ClassUnderTest_Test : public ::testing::Test, public ClassUnderTest
{
public:
    virtual void SetUp();
    virtual void TearDown();

    bool TestCase2();
};

bool ClassUnderTest_Test :: TestCase2()
{
    uint8_t retval;
    retval = ClassUnderTest::MethodToTest(1,2,3);

    return retval;
}

TEST_F( ClassUnderTest_Test , MethodToTest_test )
{
    ASSERT_EQ( TestCase2(), true );
}

In both cases ClassUnderTest.cpp.gcno is generated and inside the data seems valid, but then when I call gcovr in a following way:

python C:\Python27\Scripts\gcovr --html --html-details -o output-file-name.html

Only the coverage of TestCase1 found in the html report, TestCase2 coverage is not visible at ClassUnderTest.cpp.

What can be the problem?

Thank you in advance.