diff --git a/unit_tests/__init__.py b/unit_tests/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/unit_tests/known_issues/test_convert.py b/unit_tests/known_issues/test_convert.py
new file mode 100644
index 0000000000..0952f499fd
--- /dev/null
+++ b/unit_tests/known_issues/test_convert.py
@@ -0,0 +1,170 @@
+import os
+import sys
+import types
+import unittest
+import importlib.util
+from unittest.mock import mock_open, patch
+from xml.etree import ElementTree as ET
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", "..", "src"))
+
+
+def _load_convert():
+    sys.modules["PyQt6"] = types.ModuleType("PyQt6")
+    qtw = types.ModuleType("PyQt6.QtWidgets")
+    qtw.QErrorMessage = type("QErrorMessage", (), {})
+    qtw.QWidget = type("QWidget", (), {})
+    sys.modules["PyQt6.QtWidgets"] = qtw
+    tw = types.ModuleType("kicadtoNgspice.TrackWidget")
+    tw.TrackWidget = type("TrackWidget", (), {})
+    sys.modules["kicadtoNgspice.TrackWidget"] = tw
+    path = os.path.join(
+        os.path.dirname(__file__), "..", "..", "src", "kicadtoNgspice", "Convert.py"
+    )
+    spec = importlib.util.spec_from_file_location("kicadtoNgspice.Convert", path)
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    sys.modules["kicadtoNgspice.Convert"] = module
+    return module
+
+
+_convert = _load_convert()
+Convert = _convert.Convert
+
+
+class _MockEntry:
+    def __init__(self, text):
+        self._text = text
+
+    def text(self):
+        return self._text
+
+
+def _entries(pairs):
+    return dict((index, _MockEntry(text)) for index, text in pairs)
+
+
+class KnownIssueConverttosciform(unittest.TestCase):
+    """
+    Characterisation tests for converttosciform input sanitation.
+
+    Each test pins the CURRENT (buggy) behaviour. When a dev fixes the
+    underlying issue the assertion will fail, signalling that the test
+    should move into unit_tests/test_convert.py with the corrected
+    expectation.
+    """
+
+    def setUp(self):
+        self.convert = Convert([], {}, [], "/f/c.cir")
+
+    def test_mega_misread_as_milli(self):
+        self.assertEqual(self.convert.converttosciform("meg"), "e-03")
+
+    def test_kilo_unsupported(self):
+        self.assertEqual(self.convert.converttosciform("k"), "e-00")
+
+    def test_capital_mega_unsupported(self):
+        self.assertEqual(self.convert.converttosciform("M"), "e-00")
+
+    def test_none_falls_back_to_default(self):
+        self.assertEqual(self.convert.converttosciform(None), "e-00")
+
+    def test_non_string_raises_type_error(self):
+        with self.assertRaises(TypeError):
+            self.convert.converttosciform(123)
+
+
+class KnownIssueDefaultvalue(unittest.TestCase):
+    def setUp(self):
+        self.convert = Convert([], {}, [], "/f/c.cir")
+
+    def test_none_passes_through(self):
+        self.assertEqual(self.convert.defaultvalue(None), None)
+
+
+class KnownIssueAddSourceParameter(unittest.TestCase):
+    def test_ac_substring_in_node_name_garbles_line(self):
+        convert = Convert(
+            [[0, "ac", 0, 1]],
+            _entries([(0, "1"), (1, "0")]),
+            ["vac1 1 0 ac"],
+            "/f/c.cir",
+        )
+        self.assertEqual(convert.addSourceParameter(), ["v ac 1 0"])
+
+    def test_out_of_range_index_raises(self):
+        convert = Convert(
+            [[5, "dc", 0, 0]],
+            _entries([(0, "5")]),
+            ["v1 1 0 dc 0"],
+            "/f/c.cir",
+        )
+        with self.assertRaises(IndexError):
+            convert.addSourceParameter()
+
+    def test_missing_entry_key_is_silently_ignored(self):
+        convert = Convert(
+            [[0, "dc", 0, 0]],
+            {},
+            ["v1 1 0 dc 0"],
+            "/f/c.cir",
+        )
+        self.assertEqual(convert.addSourceParameter(), ["v1 1 0 dc 0"])
+
+
+class KnownIssueAnalysisInsertor(unittest.TestCase):
+    def _content(self, variable, acv=None, dcv=None, trv=None, acp=None,
+                 dcp=None, trp=None, ac_type="", op=None):
+        convert = Convert([], {}, [], "/fake/circuit.cir")
+        m = mock_open()
+        with patch("builtins.open", m):
+            convert.analysisInsertor(
+                acv or {},
+                dcv or {},
+                trv or {},
+                variable,
+                acp or {},
+                dcp or {},
+                trp or {},
+                ac_type,
+                op or [0],
+            )
+        return "".join(call.args[0] for call in m().write.call_args_list)
+
+    def test_dc_empty_source_name_not_defaulted(self):
+        self.assertEqual(
+            self._content(
+                "DC",
+                dcv=_entries(
+                    [(0, ""), (1, "0"), (2, "0.1"), (3, "5"), (4, ""),
+                     (5, ""), (6, ""), (7, "")]
+                ),
+                dcp={0: "V", 1: "V", 2: "V"},
+            ),
+            ".dc  0e-00 5e-00 0.1e-00",
+        )
+
+    def test_ac_empty_type_double_space(self):
+        self.assertEqual(
+            self._content(
+                "AC",
+                acv=_entries([(0, "1"), (1, "1e6"), (2, "100")]),
+                acp={0: "Hz", 1: "Meg"},
+                ac_type="",
+            ),
+            ".ac  100 1Hz 1e6Meg",
+        )
+
+
+class KnownIssueGetReferenceName(unittest.TestCase):
+    def test_missing_ref_model_raises_unbound_local(self):
+        tree = ET.fromstring("<lib><model>X</model></lib>")
+        with patch("kicadtoNgspice.Convert.ET.parse", return_value=tree):
+            with self.assertRaises(UnboundLocalError):
+                Convert([], {}, [], "/f/c.cir").getReferenceName(
+                    "2n2222.lib", "/libs"
+                )
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/unit_tests/test_convert.py b/unit_tests/test_convert.py
new file mode 100644
index 0000000000..54cefc46cc
--- /dev/null
+++ b/unit_tests/test_convert.py
@@ -0,0 +1,283 @@
+import os
+import sys
+import types
+import unittest
+import importlib.util
+from unittest.mock import mock_open, patch
+from xml.etree import ElementTree as ET
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", "src"))
+
+
+def _load_convert():
+    sys.modules["PyQt6"] = types.ModuleType("PyQt6")
+    qtw = types.ModuleType("PyQt6.QtWidgets")
+    qtw.QErrorMessage = type("QErrorMessage", (), {})
+    qtw.QWidget = type("QWidget", (), {})
+    sys.modules["PyQt6.QtWidgets"] = qtw
+    tw = types.ModuleType("kicadtoNgspice.TrackWidget")
+    tw.TrackWidget = type("TrackWidget", (), {})
+    sys.modules["kicadtoNgspice.TrackWidget"] = tw
+    path = os.path.join(
+        os.path.dirname(__file__), "..", "src", "kicadtoNgspice", "Convert.py"
+    )
+    spec = importlib.util.spec_from_file_location("kicadtoNgspice.Convert", path)
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    sys.modules["kicadtoNgspice.Convert"] = module
+    return module
+
+
+_convert = _load_convert()
+Convert = _convert.Convert
+
+
+class _MockEntry:
+    def __init__(self, text):
+        self._text = text
+
+    def text(self):
+        return self._text
+
+
+def _entries(pairs):
+    return dict((index, _MockEntry(text)) for index, text in pairs)
+
+
+class TestConverttosciform(unittest.TestCase):
+    def setUp(self):
+        self.convert = Convert([], {}, [], "/f/c.cir")
+
+    def test_milli(self):
+        self.assertEqual(self.convert.converttosciform("m"), "e-03")
+
+    def test_micro(self):
+        self.assertEqual(self.convert.converttosciform("u"), "e-06")
+
+    def test_nano(self):
+        self.assertEqual(self.convert.converttosciform("n"), "e-09")
+
+    def test_pico(self):
+        self.assertEqual(self.convert.converttosciform("p"), "e-12")
+
+    def test_empty(self):
+        self.assertEqual(self.convert.converttosciform(""), "e-00")
+
+    def test_unrecognised_unit_uses_default(self):
+        self.assertEqual(self.convert.converttosciform("V"), "e-00")
+
+
+class TestDefaultvalue(unittest.TestCase):
+    def setUp(self):
+        self.convert = Convert([], {}, [], "/f/c.cir")
+
+    def test_empty_string_defaults_to_zero(self):
+        self.assertEqual(self.convert.defaultvalue(""), 0)
+
+    def test_value_passthrough(self):
+        self.assertEqual(self.convert.defaultvalue("100"), "100")
+
+    def test_zero_passthrough(self):
+        self.assertEqual(self.convert.defaultvalue(0), 0)
+
+
+class TestAddSourceParameter(unittest.TestCase):
+    def _convert(self, track, entries, schematic):
+        return Convert(track, entries, schematic, "/f/c.cir")
+
+    def test_sine(self):
+        convert = self._convert(
+            [[0, "sine", 0, 4]],
+            _entries([(0, "1"), (1, "5"), (2, "1k"), (3, "0"), (4, "0")]),
+            ["v1 1 0 sine(0 0 0 0 0)"],
+        )
+        self.assertEqual(convert.addSourceParameter(), ["v1 1 0 sine(1 5 1k 0 0)"])
+
+    def test_sine_empty_entries_use_zero(self):
+        convert = self._convert(
+            [[0, "sine", 0, 4]],
+            _entries([(0, ""), (1, ""), (2, ""), (3, ""), (4, "")]),
+            ["v1 1 0 sine(0 0 0 0 0)"],
+        )
+        self.assertEqual(convert.addSourceParameter(), ["v1 1 0 sine(0 0 0 0 0)"])
+
+    def test_pulse(self):
+        convert = self._convert(
+            [[0, "pulse", 0, 6]],
+            _entries(
+                [(0, "0"), (1, "5"), (2, "1m"), (3, "1u"), (4, "1u"), (5, "5m"),
+                 (6, "10m")]
+            ),
+            ["v1 1 0 pulse(0 0 0 0 0 0 0)"],
+        )
+        self.assertEqual(
+            convert.addSourceParameter(), ["v1 1 0 pulse(0 5 1m 1u 1u 5m 10m)"]
+        )
+
+    def test_pwl(self):
+        convert = self._convert(
+            [[0, "pwl", 0, 0]],
+            _entries([(0, "0 0 1m 5 2m 0")]),
+            ["v1 1 0 pwl(0 0)"],
+        )
+        self.assertEqual(convert.addSourceParameter(), ["v1 1 0 pwl(0 0 1m 5 2m 0)"])
+
+    def test_pwl_empty_uses_default(self):
+        convert = self._convert(
+            [[0, "pwl", 0, 0]],
+            _entries([(0, "")]),
+            ["v1 1 0 pwl(0 0)"],
+        )
+        self.assertEqual(convert.addSourceParameter(), ["v1 1 0 pwl(0 0)"])
+
+    def test_ac(self):
+        convert = self._convert(
+            [[0, "ac", 0, 1]],
+            _entries([(0, "1"), (1, "0")]),
+            ["v1 1 0 ac"],
+        )
+        self.assertEqual(convert.addSourceParameter(), ["v1 1 0  ac 1 0"])
+
+    def test_dc(self):
+        convert = self._convert(
+            [[0, "dc", 0, 0]],
+            _entries([(0, "5")]),
+            ["v1 1 0 dc 0"],
+        )
+        self.assertEqual(convert.addSourceParameter(), ["v1 1 0  dc 5"])
+
+    def test_exp(self):
+        convert = self._convert(
+            [[0, "exp", 0, 5]],
+            _entries([(0, "0"), (1, "5"), (2, "1m"), (3, "1u"), (4, "1m"), (5, "1u")]),
+            ["v1 1 0 exp(0 0 0 0 0 0)"],
+        )
+        self.assertEqual(
+            convert.addSourceParameter(), ["v1 1 0 exp(0 5 1m 1u 1m 1u)"]
+        )
+
+    def test_multiple_sources_replaced_in_order(self):
+        convert = self._convert(
+            [[0, "sine", 0, 4], [1, "dc", 5, 5]],
+            _entries([(0, "1"), (1, "0"), (2, "1k"), (3, "0"), (4, "0"), (5, "5")]),
+            ["v1 1 0 sine(0 0 0 0 0)", "v2 2 0 dc 0"],
+        )
+        self.assertEqual(
+            convert.addSourceParameter(),
+            ["v1 1 0 sine(1 0 1k 0 0)", "v2 2 0  dc 5"],
+        )
+
+
+class TestAnalysisInsertor(unittest.TestCase):
+    def _content(self, variable, acv=None, dcv=None, trv=None, acp=None,
+                 dcp=None, trp=None, ac_type="", op=None):
+        convert = Convert([], {}, [], "/fake/circuit.cir")
+        m = mock_open()
+        with patch("builtins.open", m):
+            convert.analysisInsertor(
+                acv or {},
+                dcv or {},
+                trv or {},
+                variable,
+                acp or {},
+                dcp or {},
+                trp or {},
+                ac_type,
+                op or [0],
+            )
+        return "".join(call.args[0] for call in m().write.call_args_list)
+
+    def test_ac_dec(self):
+        self.assertEqual(
+            self._content(
+                "AC",
+                acv=_entries([(0, "1"), (1, "1e6"), (2, "100")]),
+                acp={0: "Hz", 1: "Meg"},
+                ac_type="dec",
+            ),
+            ".ac dec 100 1Hz 1e6Meg",
+        )
+
+    def test_ac_lin(self):
+        self.assertEqual(
+            self._content(
+                "AC",
+                acv=_entries([(0, "1"), (1, "1e6"), (2, "1")]),
+                acp={0: "Hz", 1: "Meg"},
+                ac_type="lin",
+            ),
+            ".ac lin 1 1Hz 1e6Meg",
+        )
+
+    def test_ac_empty_entries_default_to_zero(self):
+        self.assertEqual(
+            self._content(
+                "AC",
+                acv=_entries([(0, ""), (1, ""), (2, "")]),
+                acp={0: "Hz", 1: "Meg"},
+                ac_type="dec",
+            ),
+            ".ac dec 0 0Hz 0Meg",
+        )
+
+    def test_tran(self):
+        self.assertEqual(
+            self._content(
+                "TRAN",
+                trv=_entries([(0, "0"), (1, "0.01"), (2, "1")]),
+                trp={0: "sec", 1: "sec", 2: "sec"},
+            ),
+            ".tran 0.01e-00 1e-00 0e-00",
+        )
+
+    def test_dc(self):
+        self.assertEqual(
+            self._content(
+                "DC",
+                dcv=_entries(
+                    [(0, "V1"), (1, "0"), (2, "0.1"), (3, "5"), (4, ""),
+                     (5, ""), (6, ""), (7, "")]
+                ),
+                dcp={0: "V", 1: "V", 2: "V"},
+            ),
+            ".dc V1 0e-00 5e-00 0.1e-00",
+        )
+
+    def test_dc_two_sources(self):
+        self.assertEqual(
+            self._content(
+                "DC",
+                dcv=_entries(
+                    [(0, "V1"), (1, "0"), (2, "0.1"), (3, "5"), (4, "V2"),
+                     (5, "0"), (6, "1"), (7, "10")]
+                ),
+                dcp={0: "V", 1: "V", 2: "V", 3: "V", 4: "V", 5: "V"},
+            ),
+            ".dc V1 0e-00 5e-00 0.1e-00 V2 0e-00 10e-00 1e-00",
+        )
+
+    def test_op(self):
+        self.assertEqual(
+            self._content("DC", dcv=_entries([(0, "V1"), (1, ""), (2, ""),
+                                              (3, ""), (4, ""), (5, ""),
+                                              (6, ""), (7, "")]), op=[1]),
+            ".op",
+        )
+
+    def test_unknown_variable_writes_nothing(self):
+        self.assertEqual(self._content("NONE"), "")
+
+
+class TestGetReferenceName(unittest.TestCase):
+    def test_returns_ref_model_text(self):
+        tree = ET.fromstring("<lib><ref_model>2N2222</ref_model></lib>")
+        with patch("kicadtoNgspice.Convert.ET.parse", return_value=tree) as parse:
+            result = Convert([], {}, [], "/f/c.cir").getReferenceName(
+                "2n2222.lib", "/libs"
+            )
+        self.assertEqual(result, "2N2222")
+        parse.assert_called_once_with(os.path.join("/libs", "2n2222.xml"))
+
+
+if __name__ == "__main__":
+    unittest.main()