Refactor Unit Testing documentation

HISTORY.rst

@@ -44,12 +44,14 @@ Please check `Migration guide from 5.x to 6.0 <https://docs.platformio.org/en/la
 
 * **Unit Testing**
 
+  - New `Unit Testing <https://docs.platformio.org/en/latest/advanced/unit-testing/index.html>`_ engine and documentation
   - Added a new "test" `build configuration <https://docs.platformio.org/en/latest/projectconf/build_configurations.html>`__
   - Added support for test hierarchies (nested test suites) (`issue #4135 <https://github.com/platformio/platformio-core/issues/4135>`_)
   - Generate reports in JUnit and JSON formats using the `pio test --output-format <https://docs.platformio.org/en/latest/core/userguide/cmd_test.html#cmdoption-pio-test-output-format>`__ option  (`issue #2891 <https://github.com/platformio/platformio-core/issues/2891>`_)
   - Provide more information when the native program crashed on a host (errored with a negative return code) (`issue #3429 <https://github.com/platformio/platformio-core/issues/3429>`_)
   - Fixed an issue when command line parameters ("--ignore", "--filter") do not override values defined in the |PIOCONF| (`issue #3845 <https://github.com/platformio/platformio-core/issues/3845>`_)
   - Renamed the "test_build_project_src" project configuration option to `test_build_src <https://docs.platformio.org/en/latest//projectconf/section_env_test.html#test-build-src>`__
+  - Removed the "test_transport" option in favor of the `Custom "unity_config.h" <https://docs.platformio.org/en/latest/advanced/unit-testing/frameworks/unity.html>`_
 
 * **Static Code Analysis**
 
@@ -82,7 +84,6 @@ Please check `Migration guide from 5.x to 6.0 <https://docs.platformio.org/en/la
 * **Miscellaneous**
 
   - Improved PIO Remote setup on credit-card sized computers (Raspberry Pi, BeagleBon, etc) (`issue #3865 <https://github.com/platformio/platformio-core/issues/3865>`_)
-  - Better handling of the failed tests using the `Unit Testing <https://docs.platformio.org/en/latest/plus/unit-testing.html>`__ solution
   - Finally removed all tracks to the Python 2.7, the Python 3.6 is the minimum supported version.
 
 .. _release_notes_5: