diff --git a/HISTORY.rst b/HISTORY.rst
index 08d519a1..1a1165d9 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -48,7 +48,8 @@ Please check `Migration guide from 5.x to 6.0 <https://docs.platformio.org/en/la
   - New `Test Hierarchies <https://docs.platformio.org/en/latest/advanced/unit-testing/structure.html>`_ (`issue #4135 <https://github.com/platformio/platformio-core/issues/4135>`_)
   - New `Custom Testing Framework <https://docs.platformio.org/en/latest/advanced/unit-testing/frameworks/custom/index.html>`_
   - New "test" `build configuration <https://docs.platformio.org/en/latest/projectconf/build_configurations.html>`__
-  - Added support for ``socket://`` and ``rfc2217://`` protocols using `test_port <https://docs.platformio.org/en/latest/projectconf/section_env_test.html#test-port>`__ option (`issue #4229 <https://github.com/platformio/platformio-core/issues/4229>`_)
+  - Added support for the ``socket://`` and ``rfc2217://`` protocols using `test_port <https://docs.platformio.org/en/latest/projectconf/section_env_test.html#test-port>`__ option (`issue #4229 <https://github.com/platformio/platformio-core/issues/4229>`_)
+  - Added support for a `Custom Unity Library <https://docs.platformio.org/en/latest/advanced/unit-testing/frameworks/custom/examples/custom_unity_library.html>`__ (`issue #3980 <https://github.com/platformio/platformio-core/issues/3980>`_)
   - 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>`_)
diff --git a/docs b/docs
index 39112eef..89babce9 160000
--- a/docs
+++ b/docs
@@ -1 +1 @@
-Subproject commit 39112eefaadde9ab8e997ee485ff52a1f4bc9071
+Subproject commit 89babce984f71addb97810bc99f1d700d17f92c6
diff --git a/platformio/test/runners/factory.py b/platformio/test/runners/factory.py
index ef101d48..6c428316 100644
--- a/platformio/test/runners/factory.py
+++ b/platformio/test/runners/factory.py
@@ -42,14 +42,14 @@ class TestRunnerFactory(object):
         runner_cls = None
         if test_framework == "custom":
             test_dir = project_config.get("platformio", "test_dir")
-            custom_runner_path = os.path.join(test_dir, "custom_test_runner.py")
+            custom_runner_path = os.path.join(test_dir, "test_custom_runner.py")
             test_name = test_suite.test_name if test_suite.test_name != "*" else None
             while test_name:
                 if os.path.isfile(
-                    os.path.join(test_dir, test_name, "custom_test_runner.py")
+                    os.path.join(test_dir, test_name, "test_custom_runner.py")
                 ):
                     custom_runner_path = os.path.join(
-                        test_dir, test_name, "custom_test_runner.py"
+                        test_dir, test_name, "test_custom_runner.py"
                     )
                     break
                 test_name = os.path.dirname(test_name)  # parent dir
diff --git a/tests/commands/test_test.py b/tests/commands/test_test.py
index eb15ab69..8f3987ea 100644
--- a/tests/commands/test_test.py
+++ b/tests/commands/test_test.py
@@ -45,7 +45,7 @@ def test_calculator_example(tmp_path: Path):
 
     # test JUnit output
     junit_testsuites = ET.parse(junit_output_path).getroot()
-    assert int(junit_testsuites.get("tests")) == 10
+    assert int(junit_testsuites.get("tests")) == 11
     assert int(junit_testsuites.get("errors")) == 2
     assert int(junit_testsuites.get("failures")) == 1
     assert len(junit_testsuites.findall("testsuite")) == 6
@@ -112,7 +112,7 @@ void my_extra_fun(void) {
     # test group
     test_group = test_dir / "group"
     test_group.mkdir(parents=True)
-    (test_group / "custom_test_runner.py").write_text(
+    (test_group / "test_custom_runner.py").write_text(
         """
 import click