Set up pytest and coverage tooling

pyproject.toml

@@ -17,7 +17,9 @@ dependencies = [
 dev = [
     "beartype",
     "black",
+    "coverage",
     "mypy",
+    "pytest",
     "types-PyYAML",
     "types-Pygments",
 ]
@@ -31,6 +33,15 @@ target-version = ["py314"]
 [tool.mypy]
 strict = true
 
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+
+[tool.coverage.run]
+source = ["omicron"]
+
+[tool.coverage.report]
+show_missing = true
+
 [tool.setuptools.packages.find]
 where = ["."]
 include = ["omicron.ssg*"]