python3Packages.spherogram: add sage tests

see
https://github.com/3-manifolds/Spherogram/blob/2.4_as_released/.github/workflows/test.yml#L36

pkgs/development/python-modules/spherogram/default.nix

@@ -14,6 +14,11 @@
   networkx,
   snappy-15-knots,
   snappy-manifolds,
+
+  # tests
+  runCommand,
+  sage,
+  writableTmpDirAsHomeHook,
 }:
 
 buildPythonPackage rec {
@@ -50,6 +55,25 @@ buildPythonPackage rec {
     runHook postCheck
   '';
 
+  passthru.tests.sage =
+    let
+      sage' = sage.override {
+        extraPythonPackages = ps: [ ps.spherogram ];
+        requireSageTests = false;
+      };
+    in
+    runCommand "spherogram-sage-tests"
+      {
+        nativeBuildInputs = [
+          sage'
+          writableTmpDirAsHomeHook
+        ];
+      }
+      ''
+        sage -python -m spherogram.test
+        touch $out
+      '';
+
   meta = {
     description = "Spherical diagrams for 3-manifold topology";
     homepage = "https://snappy.computop.org/spherogram.html";