fix: DataSource abstract method for Octave, resilient test runner

- Replace methods (Abstract) with runtime error (Octave doesn't
  support Abstract methods block)
- Make CI test runner resilient to Octave cleanup crashes: save
  results to file before potential crash, check results from shell

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: HanSur94

.github/workflows/tests.yml

@@ -75,7 +75,30 @@ jobs:
 
       - name: Run tests
         run: |
-          xvfb-run octave --eval "cd('tests'); r = run_all_tests(); if r.failed > 0; exit(1); end"
+          # Octave 8.x has a known crash during handle class cleanup
+          # (break_closure_cycles: invalid object). Run tests and capture
+          # the results file before any potential crash.
+          xvfb-run octave --eval "
+            cd('tests');
+            r = run_all_tests();
+            fid = fopen('/tmp/test-results.txt', 'w');
+            fprintf(fid, '%d %d\n', r.passed, r.failed);
+            fclose(fid);
+            if r.failed > 0; exit(1); end
+          " || true
+          # Check results even if Octave crashed during cleanup
+          if [ -f /tmp/test-results.txt ]; then
+            read passed failed < /tmp/test-results.txt
+            echo "Results: $passed passed, $failed failed"
+            if [ "$failed" -gt 0 ]; then
+              echo "::error::$failed test(s) failed"
+              exit 1
+            fi
+            echo "All $passed tests passed (Octave may have crashed during cleanup — known bug)"
+          else
+            echo "::error::Octave crashed before completing tests"
+            exit 1
+          fi
 
   mex-build-macos:
     name: MEX Build (macOS)

libs/EventDetection/DataSource.m

@@ -8,8 +8,10 @@
     %     .stateY  — 1xK state values (empty if none)
     %     .changed — logical, true if new data since last call
 
-    methods (Abstract)
-        result = fetchNew(obj)
+    methods
+        function result = fetchNew(obj) %#ok<STOUT>
+            error('DataSource:abstract', 'fetchNew must be implemented by subclass');
+        end
     end
 
     methods (Static)