Should i put unit tests in a separate library? Separate subdirectory?

Question

I have a large library of code which has a few (much too few) unit tests; i am adding code to the library, trying to make unit tests for the new code (i also want to add unit tests for old code in future, when i get more experienced).

We currently use a custom (not very elaborate) unit-testing framework; i would like to switch to boost.test.

My library layout is:

• mylib1 (300 files, 70000 lines of code)

  • src
    • foo
      • foo.cpp
      • foo_part.cpp
      • foo_part.h
      • UnitTests - should i move it outside mylib?
        • foo_test1.cpp
        • foo_test2.cpp
        • foo_test3.cpp
    • bar
      • bar.cpp
      • bar_part.cpp
      • bar_part.h
      • UnitTests - does it belong here?
        • bar_test1.cpp
        • bar_test2.cpp
        • bar_test3.cpp
  • include
    • foo.h
    • bar.h

• mylib2 (70 files, 7000 lines of code)

  • Looks like the mylib1 above

• UnitTestFramework

  • src
    • MockObject1.cpp - does it belong here?
    • Asserter.cpp - boost.test will replace it
    • TestFixture.cpp - boost.test will replace it
  • include
    • MockObject1.h
    • Asserter.h - boost.test will replace it
    • TestFixture.h - boost.test will replace it

I am asking the following questions here:

• Should unit tests be part of mylib DLL? (I link mylib1 and mylib2 into one DLL)
• Should source code for unit tests be located under the mylib1 directory?
• Since i have mylib1 and mylib2, how should the corresponding unit-tests be located - in sibling directories, together, etc?
• Where should i put source code for mock objects? (they serve both mylib1 and mylib2)

Answer 1

1. unit tests are kind of documentation, therefore I would leave the directory structure as it is
2. mocks/fakes are helpers in unit tests, therefore I wouldn't leave them in the source directory. Create a new directory in the source, and move them there.

Actually, I would simplify it even further :

 + mylib1 (300 files, 70000 lines of code)
    + unit_tests
      + test_foo.cpp
      + test_bar.cpp
    + mocks
      + mock_foo.hpp
      + mock_bar.hpp
    + foo.cpp
    + foo.hpp
    + bar.cpp
    + bar.hpp
 + mylib2
similar as for mylib1