diff --git a/testing/backend/unit/test_port_scanner_helpers.py b/testing/backend/unit/test_port_scanner_helpers.py
new file mode 100644
index 00000000..011452a3
--- /dev/null
+++ b/testing/backend/unit/test_port_scanner_helpers.py
@@ -0,0 +1,153 @@
+"""
+Unit tests for PortScanner input-resolution static helpers in
+backend/secuscan/scanners/port_scanner.py.
+
+Covers:
+- _resolve_scan_type: normalises scan type spec to nmap plugin SELECT value (S/T/U)
+- _resolve_ports: normalises port shorthand to nmap port range string
+
+run() and _parse_nmap_output() perform real I/O and are NOT tested here.
+"""
+
+import pytest
+
+from backend.secuscan.scanners.port_scanner import PortScanner
+
+
+# ---------------------------------------------------------------------------
+# _resolve_scan_type
+# ---------------------------------------------------------------------------
+
+
+class TestResolveScanType:
+    def test_bare_S(self):
+        assert PortScanner._resolve_scan_type("S") == "S"
+
+    def test_bare_T(self):
+        assert PortScanner._resolve_scan_type("T") == "T"
+
+    def test_bare_U(self):
+        assert PortScanner._resolve_scan_type("U") == "U"
+
+    def test_lowercase_s(self):
+        assert PortScanner._resolve_scan_type("s") == "S"
+        assert PortScanner._resolve_scan_type("t") == "T"
+        assert PortScanner._resolve_scan_type("u") == "U"
+
+    def test_dash_prefixed_sT(self):
+        assert PortScanner._resolve_scan_type("-sT") == "T"
+
+    def test_dash_prefixed_sS(self):
+        assert PortScanner._resolve_scan_type("-sS") == "S"
+
+    def test_dash_prefixed_sU(self):
+        assert PortScanner._resolve_scan_type("-sU") == "U"
+
+    def test_dash_prefixed_uppercase(self):
+        assert PortScanner._resolve_scan_type("-ST") == "T"
+
+    def test_bare_sT_no_dash(self):
+        assert PortScanner._resolve_scan_type("sT") == "T"
+
+    def test_bare_sS_no_dash(self):
+        assert PortScanner._resolve_scan_type("sS") == "S"
+
+    def test_empty_string_defaults_to_T(self):
+        assert PortScanner._resolve_scan_type("") == "T"
+
+    def test_none_defaults_to_T(self):
+        assert PortScanner._resolve_scan_type(None) == "T"
+
+    def test_whitespace_stripped(self):
+        assert PortScanner._resolve_scan_type("  T  ") == "T"
+
+    def test_invalid_scan_type_raises(self):
+        with pytest.raises(ValueError, match="Invalid scan_type"):
+            PortScanner._resolve_scan_type("X")
+
+    def test_invalid_dash_prefix_raises(self):
+        with pytest.raises(ValueError, match="Invalid scan_type"):
+            PortScanner._resolve_scan_type("-sX")
+
+    def test_invalid_bare_letter_raises(self):
+        with pytest.raises(ValueError, match="Invalid scan_type"):
+            PortScanner._resolve_scan_type("V")
+
+    def test_multi_char_non_strippable_raises(self):
+        with pytest.raises(ValueError, match="Invalid scan_type"):
+            PortScanner._resolve_scan_type("scan")
+
+    def test_partial_dash_strip_raises(self):
+        with pytest.raises(ValueError, match="Invalid scan_type"):
+            PortScanner._resolve_scan_type("-s")
+
+
+# ---------------------------------------------------------------------------
+# _resolve_ports
+# ---------------------------------------------------------------------------
+
+
+class TestResolvePorts:
+    def test_none_returns_empty_string(self):
+        assert PortScanner._resolve_ports(None) == ""
+
+    def test_empty_string_returns_empty_string(self):
+        assert PortScanner._resolve_ports("") == ""
+
+    def test_top100_returns_empty_string(self):
+        # top100 maps to empty string to use plugin default (top-100 ports)
+        assert PortScanner._resolve_ports("top100") == ""
+
+    def test_top1000_returns_one_to_1000(self):
+        assert PortScanner._resolve_ports("top1000") == "1-1000"
+
+    def test_all_returns_one_to_65535(self):
+        assert PortScanner._resolve_ports("all") == "1-65535"
+
+    def test_single_port_passthrough(self):
+        assert PortScanner._resolve_ports("80") == "80"
+        assert PortScanner._resolve_ports("443") == "443"
+        assert PortScanner._resolve_ports("8080") == "8080"
+
+    def test_port_range_passthrough(self):
+        assert PortScanner._resolve_ports("1-1000") == "1-1000"
+        assert PortScanner._resolve_ports("22-1024") == "22-1024"
+
+    def test_comma_separated_ports_passthrough(self):
+        assert PortScanner._resolve_ports("22,80,443") == "22,80,443"
+
+    def test_comma_separated_ranges_passthrough(self):
+        assert PortScanner._resolve_ports("22,80-90,443,8000-8100") == "22,80-90,443,8000-8100"
+
+    def test_whitespace_not_stripped_raises(self):
+        # _resolve_ports does NOT strip whitespace; raw input must be exact
+        with pytest.raises(ValueError, match="Invalid port specification"):
+            PortScanner._resolve_ports("  80  ")
+
+    def test_invalid_non_numeric_raises(self):
+        with pytest.raises(ValueError, match="Invalid port specification"):
+            PortScanner._resolve_ports("http")
+
+    def test_invalid_mixed_format_raises(self):
+        with pytest.raises(ValueError, match="Invalid port specification"):
+            PortScanner._resolve_ports("80-abc")
+
+    def test_range_order_not_validated_by_function(self):
+        # The function uses a regex that accepts "100-80" as a valid port spec.
+        # Range-order validation is the caller's responsibility.
+        assert PortScanner._resolve_ports("100-80") == "100-80"
+
+    def test_range_order_reversed_accepted(self):
+        assert PortScanner._resolve_ports("1024-22") == "1024-22"
+
+    def test_invalid_single_value_letters_raises(self):
+        with pytest.raises(ValueError, match="Invalid port specification"):
+            PortScanner._resolve_ports("abc")
+
+    def test_invalid_topxxx_raises(self):
+        with pytest.raises(ValueError, match="Invalid port specification"):
+            PortScanner._resolve_ports("top50")
+
+    def test_negative_port_raises(self):
+        with pytest.raises(ValueError, match="Invalid port specification"):
+            PortScanner._resolve_ports("-1")
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