Set up testing with pytest and co

nix/package.nix

@@ -29,6 +29,14 @@ python3Packages.buildPythonApplication {
     sqlalchemy
   ];
 
+  pythonImportsCheck = [];
+
+  doCheck = true;
+  nativeCheckInputs = with python3Packages; [
+    pytest
+    pytestCheckHook
+  ];
+
   postInstall = ''
     wrapProgram $out/bin/dibbler \
       --prefix PATH : "${lib.makeBinPath [ less ]}"

nix/shell.nix

@@ -1,6 +1,6 @@
 {
   mkShell,
-  python,
+  python3,
   ruff,
   uv,
 }:
@@ -9,12 +9,16 @@ mkShell {
   packages = [
     ruff
     uv
-    (python.withPackages (ps: with ps; [
+    (python3.withPackages (ps: with ps; [
       brother-ql
       matplotlib
       psycopg2
       python-barcode
       sqlalchemy
+      sqlparse
+
+      pytest
+      pytest-cov
     ]))
   ];
 }