tests: move testing stuff into its own directory

pyproject.toml

@@ -48,6 +48,7 @@ dev = [
   "pytest>=9.0.1",
   "pytest-asyncio>=1.3.0",
   "pytest-cov>=7.0.0",
+  "pytest-sugar>=1.1.1",
   "pytest-textual-snapshot>=1.0.0",
   "textual-dev>=1.8.0",
   "twine>=6.2.0",
@@ -59,11 +60,17 @@ build-backend = "uv_build"
 
 [tool.coverage.run]
 branch = true
-omit = ["tests.py"]
+omit = ["tests/"]
 source_dirs = ["src/"]
 
-[tool.pytest]
 # custom marks are created in conftest.py
+[tool.pytest]
+python_files = ["*_test.py", "test_*.py", "tests.py"]
+strict_config = true
+strict_markers = true
+strict_parametrization_ids = false
+strict_xfail = true
+testpaths = ["testing/"]
 asyncio_mode = "auto"
 
 [tool.ruff]