Importer logs warning if no data could be imported

VERSION

@@ -1 +1 @@
-0.12.0.dev53
+0.12.0.dev54

aspecd/io.py

@@ -457,7 +457,8 @@ def import_into(self, dataset=None):
         else:
             self.dataset = dataset
         self._import()
-        # Untested due to lack of ideas how to test
+        if self.dataset.data.data.size == 0:
+            logger.warning('Could not read data from "%s"', self.source)
         # pylint: disable=protected-access
         self.dataset._origdata = copy.deepcopy(self.dataset.data)
         self.dataset.id = self.source

tests/test_io.py

@@ -65,6 +65,28 @@ def test_import_into_does_not_override_label(self):
         self.importer.import_into(test_dataset)
         self.assertEqual("foobar", test_dataset.label)
 
+    def test_import_copies_data_to_origdata(self):
+        class MockImporter(io.DatasetImporter):
+            def _import(self):
+                self.dataset.data.data = np.ones(5)
+
+        test_dataset = dataset.Dataset()
+        importer = MockImporter()
+        importer.source = "foobar"
+        importer.import_into(test_dataset)
+        np.testing.assert_array_equal(
+            test_dataset.data.data, test_dataset._origdata.data
+        )
+
+    def test_import_with_no_data_read_logs_warning(self):
+        test_dataset = dataset.Dataset()
+        self.importer.source = "/path/to/filename.ext"
+        with self.assertLogs(__package__, level="WARN") as cm:
+            self.importer.import_into(test_dataset)
+        self.assertIn(
+            f'Could not read data from "{self.importer.source}"', cm.output[0]
+        )
+
 
 class TestDatasetExporter(unittest.TestCase):
     def setUp(self):