test(pytest-plugin): add plugin tests

Cover validate_text assertions, fixture factories, marker registration,
and pytest integration using pytester for subprocess testing.

tests/test_pytest_plugin/test_plugin.py

@@ -0,0 +1,100 @@
+"""Tests for the pytest plugin hooks."""
+
+import pytest
+
+
+@pytest.fixture
+def plugin_pytester(pytester: pytest.Pytester) -> pytest.Pytester:
+    """Configure pytester to use the veritext plugin."""
+    pytester.makeconftest(
+        """
+        pytest_plugins = ['veritext.pytest_plugin']
+        """
+    )
+    return pytester
+
+
+def test_plugin_registers_marker(plugin_pytester: pytest.Pytester) -> None:
+    """Test that the text_validation marker is registered."""
+    plugin_pytester.makepyfile(
+        """
+        import pytest
+
+        @pytest.mark.text_validation
+        def test_example():
+            pass
+        """
+    )
+    # Run with strict markers - this will fail if marker isn't registered
+    result = plugin_pytester.runpytest("--strict-markers")
+    result.assert_outcomes(passed=1)
+
+
+def test_marker_can_be_used(plugin_pytester: pytest.Pytester) -> None:
+    """Test that the text_validation marker can filter tests."""
+    plugin_pytester.makepyfile(
+        """
+        import pytest
+
+        @pytest.mark.text_validation
+        def test_marked():
+            pass
+
+        def test_unmarked():
+            pass
+        """
+    )
+    # Run only marked tests
+    result = plugin_pytester.runpytest("-m", "text_validation")
+    result.assert_outcomes(passed=1)
+
+
+def test_validate_text_is_importable(plugin_pytester: pytest.Pytester) -> None:
+    """Test that validate_text can be imported from the plugin."""
+    plugin_pytester.makepyfile(
+        """
+        from veritext.pytest_plugin import validate_text
+
+        def test_import():
+            assert callable(validate_text)
+        """
+    )
+    result = plugin_pytester.runpytest()
+    result.assert_outcomes(passed=1)
+
+
+def test_validate_text_works_in_tests(plugin_pytester: pytest.Pytester) -> None:
+    """Test that validate_text can be used in test functions."""
+    plugin_pytester.makepyfile(
+        """
+        from veritext.pytest_plugin import validate_text
+
+        def test_validation_passes():
+            validate_text(
+                "The quick brown fox jumps over the lazy dog.",
+                min_length=10,
+                max_length=100,
+            )
+        """
+    )
+    result = plugin_pytester.runpytest()
+    result.assert_outcomes(passed=1)
+
+
+def test_validate_text_failure_in_tests(plugin_pytester: pytest.Pytester) -> None:
+    """Test that validate_text failures are reported properly."""
+    plugin_pytester.makepyfile(
+        """
+        from veritext.pytest_plugin import validate_text
+
+        def test_validation_fails():
+            validate_text(
+                "Short",
+                min_length=100,
+            )
+        """
+    )
+    result = plugin_pytester.runpytest()
+    result.assert_outcomes(failed=1)
+    # Check that failure message contains useful information
+    result.stdout.fnmatch_lines(["*Text validation failed*"])