diff --git a/pypact/input/inputdata.py b/pypact/input/inputdata.py
index 7971506..8e00f59 100644
--- a/pypact/input/inputdata.py
+++ b/pypact/input/inputdata.py
@@ -425,6 +425,30 @@ 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.setMass(float(parts[1]))
+                num_elements = int(parts[2])
+                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.addElement(element, float(percentage))
+                    num_elements -= 1
+                    if num_elements == 0:
+                        in_mass_section = False
+                else:
+                    raise PypactInvalidOptionException("Invalid element line format in MASS section.")
\ No newline at end of file
diff --git a/reference/test.i b/reference/test.i
new file mode 100644
index 0000000..48d4c39
--- /dev/null
+++ b/reference/test.i
@@ -0,0 +1,63 @@
+<< CONTROL PHASE >>
+<< enable JSON output >>
+JSON 
+<< overwrite existing output files of same name >>
+CLOBBER 
+<< read gamma groups from file, specify ggbins in files file >>
+READGG 
+<< monitor FISPACT-II progress >>
+MONITOR 1
+<< the minimum cross section (barns) for inclusion in pathways analysis >>
+XSTHRESHOLD 1e-12
+<< perform collapse >>
+GETXS 1 709
+<< get decay data >>
+GETDECAY 1
+<< enable logging at level 1 >>
+LOGLEVEL 1
+<< approximate spectra when not available >>
+SPEK 
+<< end control >>
+FISPACT 
+* test
+
+<< INITIALIZATION PHASE >>
+<< output half life values >>
+HALF 
+<< output ingestion and inhalation values >>
+HAZARDS 
+<< set the target via MASS >>
+MASS 1.0 3
+Ti 80.0
+Fe 14.8
+Cr 5.2 
+<< set the target density >>
+DENSITY 19.5
+<< set the threshold for atoms in the inventory >>
+MIND 100000.0
+<< output the initial inventory >>
+ATOMS 
+
+<< INVENTORY PHASE >>
+<< irradiation schedule >>
+FLUX 1100000000000000.0
+TIME 300.0 SECS
+ATOMS 
+<< end of irradiation >>
+FLUX 0.0
+ZERO 
+TIME 10.0 SECS
+ATOMS 
+TIME 100.0 SECS
+ATOMS 
+TIME 1000.0 SECS
+ATOMS 
+TIME 10000.0 SECS
+ATOMS 
+TIME 100000.0 SECS
+ATOMS 
+<< end of cooling >>
+
+<< end of input >>
+END 
+* end
diff --git a/tests/input/inputfiletest.py b/tests/input/inputfiletest.py
new file mode 100644
index 0000000..7dc92db
--- /dev/null
+++ b/tests/input/inputfiletest.py
@@ -0,0 +1,30 @@
+import pypact as pp
+
+from tests.testerbase import Tester
+
+
+class InputFileTest(Tester):
+
+    def test_reading_in_mass(self):
+        ff = pp.InputData()
+        pp.from_file(ff, 'reference/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}"
\ No newline at end of file
diff --git a/tests/testsuite.py b/tests/testsuite.py
index 99f2cda..8391c46 100644
--- a/tests/testsuite.py
+++ b/tests/testsuite.py
@@ -23,6 +23,7 @@
 from tests.input.groupconverttest import GroupConvertUnitTest
 from tests.input.groupstructurestest import GroupStructuresUnitTest
 from tests.input.projectilestest import ProjectilesUnitTest
+from tests.input.inputfiletest import InputFileTest 
 
 from tests.library.nuclidelibtest import NuclideLibUnitTest
 from tests.library.reactionlibtest import ReactionLibUnitTest