TestFunctions.o: In function `test1()':
/in/compile/TestFunctions.cpp:97: undefined reference to `operator<<(std::ostream&, BinaryTree const&)'
TestFunctions.o: In function `test4()':
/in/compile/TestFunctions.cpp:118: undefined reference to `operator<<(std::ostream&, BinaryTree const&)'
TestFunctions.o: In function `test8()':
/in/compile/TestFunctions.cpp:154: undefined reference to `operator<<(std::ostream&, BinaryTree const&)'
TestFunctions.o: In function `test9()':
/in/compile/TestFunctions.cpp:166: undefined reference to `operator<<(std::ostream&, BinaryTree const&)'
TestFunctions.o: In function `test10()':
/in/compile/TestFunctions.cpp:178: undefined reference to `operator<<(std::ostream&, BinaryTree const&)'
TestFunctions.o:/in/compile/TestFunctions.cpp:200: more undefined references to `operator<<(std::ostream&, BinaryTree const&)' follow
collect2: error: ld returned 1 exit status
/in/compile/Makefile:56: recipe for target 'test' failed
make: *** [test] Error 1