How to do unit testing on private members (and methods) of C++ classes [duplicate]

Answer 1

Example from the google testing framework:

// foo.h
#include "gtest/gtest_prod.h"
class Foo {
  ...
 private:
  FRIEND_TEST(FooTest, BarReturnsZeroOnNull);
  int Bar(void* x);
};

// foo_test.cc
...
TEST(FooTest, BarReturnsZeroOnNull) {
  Foo foo;
  EXPECT_EQ(0, foo.Bar(NULL));
  // Uses Foo's private member Bar().
}

The main idea is the use of the friend cpp keyword. You can extend this example as following:

// foo.h
#ifdef TEST_FOO
#include "gtest/gtest_prod.h"
#endif

class Foo {
  ...
 private:
  #ifdef TEST_FOO
  FRIEND_TEST(FooTest, BarReturnsZeroOnNull);
  #endif
  int Bar(void* x);
};

You can define the TEST_FOO preprocessor in two ways:

1)within the CMakeLists.txt

option(TEST "Run test ?" ON)
if (TEST)
  add_definitions(-DTEST_FOO)
endif()

2)as arguments to your compiler

g++ -D TEST $your_args