added mass reading and test

pypact/input/inputdata.py

@@ -425,6 +425,32 @@ def _deserialize(self, f):
             The deserialization method
             f: file object
         """
-        pass
-
-
+        self.reset()
+
+        lines = f.readlines()
+        in_mass_section = False
+
+        for line in lines:
+            line = line.strip()
+            if line.startswith("MASS"):
+                # Parse the MASS line
+                parts = line.split()
+                if len(parts) < 3:
+                    raise PypactInvalidOptionException("Invalid MASS line format.")
+                self._inventoryismass = True
+                self._inventorymass.totalMass = float(parts[1])
+                num_elements = int(parts[2])
+                self._inventorymass.entries = []
+                in_mass_section = True
+                continue
+
+            if in_mass_section:
+                # Parse the elements following the MASS line
+                if len(line.split()) == 2:
+                    element, percentage = line.split()
+                    self._inventorymass.entries.append((element, float(percentage)))
+                    num_elements -= 1
+                    if num_elements == 0:
+                        in_mass_section = False
+                else:
+                    raise PypactInvalidOptionException("Invalid element line format in MASS section.")

tests/input/inputfiletest.py

@@ -0,0 +1,26 @@
+import pypact as pp
+
+
+def test_reading_in_mass():
+    ff = pp.InputData()
+    pp.from_file(ff, 'examples/files/test.i')
+
+    # Assert that the inventory is set to mass mode
+    assert ff._inventoryismass is True, "Inventory should be set to mass mode"
+    assert ff._inventoryisfuel is False, "Inventory should not be set to fuel mode"
+
+    # Assert the total mass
+    assert ff._inventorymass.totalMass == 1.0, "Total mass should be 1.0"
+
+    # Assert the number of elements
+    assert len(ff._inventorymass.entries) == 3, "There should be 3 elements in the inventory"
+
+    # Assert the elements and their percentages
+    expected_elements = [
+        ("Ti", 80.0),
+        ("Fe", 14.8),
+        ("Cr", 5.2)
+    ]
+    for i, (element, percentage) in enumerate(expected_elements):
+        assert ff._inventorymass.entries[i][0] == element, f"Element {i} should be {element}"
+        assert ff._inventorymass.entries[i][1] == percentage, f"Percentage of {element} should be {percentage}"