ENH: make OutputChecker pluggable in the doctest layer

Author: ev-br

scpdt/impl.py

@@ -85,6 +85,7 @@ class DTConfig:
         a string. If not empty, the string value is used as the skip reason.
     """
     def __init__(self, *, # DTChecker configuration
+                          CheckerKlass=None,
                           default_namespace=None,
                           check_namespace=None,
                           rndm_markers=None,
@@ -108,6 +109,8 @@ def __init__(self, *, # DTChecker configuration
                           pytest_extra_xfail=None,
     ):
         ### DTChecker configuration ###
+        self.CheckerKlass = CheckerKlass or DTChecker
+
         # The namespace to run examples in
         self.default_namespace = default_namespace or {}
 
@@ -340,7 +343,7 @@ def __init__(self, checker=None, verbose=None, optionflags=None, config=None):
         if config is None:
             config = DTConfig()
         if checker is None:
-            checker = DTChecker(config)
+            checker = config.CheckerKlass(config)
         self.nameerror_after_exception = config.nameerror_after_exception
         if optionflags is None:
             optionflags = config.optionflags

scpdt/tests/test_runner.py

@@ -4,8 +4,10 @@
 
 import pytest
 
-from . import failure_cases as module, finder_cases as finder_module
-from .. import DTFinder, DTRunner, DebugDTRunner
+from . import (failure_cases as module,
+               finder_cases as finder_module,
+               module_cases)
+from .. import DTFinder, DTRunner, DebugDTRunner, DTConfig
 
 
 ### Smoke test DTRunner methods. Mainly to check that they are runnable.
@@ -79,3 +81,25 @@ def test_debug_runner_exception(self):
         # exception carries the original test
         assert orig_exception.test is tests[0]
 
+
+class VanillaOutputChecker(doctest.OutputChecker):
+    """doctest.OutputChecker to drop in for DTChecker.
+
+    LSP break: OutputChecker does not have __init__,
+    here we add it to agree with DTChecker.
+    """
+    def __init__(self, config):
+        pass
+
+class TestCheckerDropIn:
+    """Test DTChecker and vanilla doctest OutputChecker being drop-in replacements.
+    """
+    def test_vanilla_checker(self):
+        config = DTConfig(CheckerKlass=VanillaOutputChecker)
+        runner = DebugDTRunner(config=config)
+        tests = DTFinder().find(module_cases.func)
+
+        with pytest.raises(doctest.DocTestFailure) as exc:
+            for t in tests:
+                runner.run(t)
+