diff --git a/src/Mod/Path/Generators/helix_generator.py b/src/Mod/Path/Generators/helix_generator.py
index 89b3ce13bb..3d860da39b 100644
--- a/src/Mod/Path/Generators/helix_generator.py
+++ b/src/Mod/Path/Generators/helix_generator.py
@@ -56,6 +56,11 @@ def generate(
     startPoint = edge.Vertexes[0].Point
     endPoint = edge.Vertexes[1].Point
 
+    # Swap start and end points if edge line is inverted
+    if startPoint.z < endPoint.z:
+        endPoint = edge.Vertexes[0].Point
+        startPoint = edge.Vertexes[1].Point
+
     PathLog.track(
         "(helix: <{}, {}>\n hole radius {}\n inner radius {}\n step over {}\n start point {}\n end point {}\n step_down {}\n tool diameter {}\n direction {}\n startat {})".format(
             startPoint.x,
diff --git a/src/Mod/Path/PathTests/TestPathHelixGenerator.py b/src/Mod/Path/PathTests/TestPathHelixGenerator.py
index d21bf0c987..469d101d28 100644
--- a/src/Mod/Path/PathTests/TestPathHelixGenerator.py
+++ b/src/Mod/Path/PathTests/TestPathHelixGenerator.py
@@ -20,18 +20,164 @@
 # *                                                                         *
 # ***************************************************************************
 
-import Path
 import FreeCAD
-import Generators.helix_generator as generator
-import PathScripts.PathLog as PathLog
-import PathTests.PathTestUtils as PathTestUtils
 import Part
+import Path
+import PathScripts.PathLog as PathLog
+import Generators.helix_generator as generator
+import PathTests.PathTestUtils as PathTestUtils
+
 
 PathLog.setLevel(PathLog.Level.INFO, PathLog.thisModule())
 PathLog.trackModule(PathLog.thisModule())
 
 
+def _resetArgs():
+    v1 = FreeCAD.Vector(5, 5, 20)
+    v2 = FreeCAD.Vector(5, 5, 10)
+
+    edg = Part.makeLine(v1, v2)
+
+    return {
+        "edge": edg,
+        "hole_radius": 10.0,
+        "step_down": 1.0,
+        "step_over": 5.0,
+        "tool_diameter": 5.0,
+        "inner_radius": 0.0,
+        "direction": "CW",
+        "startAt": "Inside",
+    }
+
+
 class TestPathHelixGenerator(PathTestUtils.PathTestBase):
+    expectedHelixGCode = "G0 X12.500000 Y5.000000\
+G1 Z20.000000\
+G2 I-7.500000 J0.000000 X-2.500000 Y5.000000 Z19.500000\
+G2 I7.500000 J0.000000 X12.500000 Y5.000000 Z19.000000\
+G2 I-7.500000 J0.000000 X-2.500000 Y5.000000 Z18.500000\
+G2 I7.500000 J0.000000 X12.500000 Y5.000000 Z18.000000\
+G2 I-7.500000 J0.000000 X-2.500000 Y5.000000 Z17.500000\
+G2 I7.500000 J0.000000 X12.500000 Y5.000000 Z17.000000\
+G2 I-7.500000 J0.000000 X-2.500000 Y5.000000 Z16.500000\
+G2 I7.500000 J0.000000 X12.500000 Y5.000000 Z16.000000\
+G2 I-7.500000 J0.000000 X-2.500000 Y5.000000 Z15.500000\
+G2 I7.500000 J0.000000 X12.500000 Y5.000000 Z15.000000\
+G2 I-7.500000 J0.000000 X-2.500000 Y5.000000 Z14.500000\
+G2 I7.500000 J0.000000 X12.500000 Y5.000000 Z14.000000\
+G2 I-7.500000 J0.000000 X-2.500000 Y5.000000 Z13.500000\
+G2 I7.500000 J0.000000 X12.500000 Y5.000000 Z13.000000\
+G2 I-7.500000 J0.000000 X-2.500000 Y5.000000 Z12.500000\
+G2 I7.500000 J0.000000 X12.500000 Y5.000000 Z12.000000\
+G2 I-7.500000 J0.000000 X-2.500000 Y5.000000 Z11.500000\
+G2 I7.500000 J0.000000 X12.500000 Y5.000000 Z11.000000\
+G2 I-7.500000 J0.000000 X-2.500000 Y5.000000 Z10.500000\
+G2 I7.500000 J0.000000 X12.500000 Y5.000000 Z10.000000\
+G2 I-7.500000 J0.000000 X-2.500000 Y5.000000 Z10.000000\
+G2 I7.500000 J0.000000 X12.500000 Y5.000000 Z10.000000\
+G0 X5.000000 Y5.000000 Z20.000000"
+
     def test00(self):
         """Test Basic Helix Generator Return"""
-        self.assertTrue(True)
+        args = _resetArgs()
+        result = generator.generate(**args)
+        self.assertTrue(type(result) is list)
+        self.assertTrue(type(result[0]) is Path.Command)
+
+        gcode = "".join([r.toGCode() for r in result])
+        self.assertTrue(
+            gcode == self.expectedHelixGCode, "Incorrect helix g-code generated"
+        )
+
+    def test01(self):
+        """Test Basic Helix Generator hole_radius is float > 0"""
+        args = _resetArgs()
+        args["hole_radius"] = 10
+        self.assertRaises(ValueError, generator.generate, **args)
+
+        args["hole_radius"] = -10.0
+        self.assertRaises(ValueError, generator.generate, **args)
+
+    def test02(self):
+        """Test Basic Helix Generator inner_radius is float"""
+        args = _resetArgs()
+        args["inner_radius"] = 2
+        self.assertRaises(ValueError, generator.generate, **args)
+
+    def test03(self):
+        """Test Basic Helix Generator tool_diameter is float"""
+        args = _resetArgs()
+        args["tool_diameter"] = 5
+        self.assertRaises(ValueError, generator.generate, **args)
+
+    def test04(self):
+        """Test Basic Helix Generator tool fit with radius difference less than tool diameter"""
+        args = _resetArgs()
+        # require tool fit 1: radius diff less than tool diam
+        args["hole_radius"] = 10.0
+        args["inner_radius"] = 6.0
+        args["tool_diameter"] = 5.0
+        self.assertRaises(ValueError, generator.generate, **args)
+
+        # require tool fit 2: hole radius less than tool diam with zero inner radius
+        args["hole_radius"] = 4.5
+        args["inner_radius"] = 0.0
+        args["tool_diameter"] = 5.0
+        self.assertRaises(ValueError, generator.generate, **args)
+
+    def test05(self):
+        """Test Basic Helix Generator validate the startAt enumeration value"""
+        args = _resetArgs()
+        args["startAt"] = "Other"
+        self.assertRaises(ValueError, generator.generate, **args)
+
+    def test06(self):
+        """Test Basic Helix Generator validate the direction enumeration value"""
+        args = _resetArgs()
+        args["direction"] = "clock"
+        self.assertRaises(ValueError, generator.generate, **args)
+
+    def test07(self):
+        """Test Basic Helix Generator verify linear edge is vertical"""
+        # verify linear edge is vertical: X
+        args = _resetArgs()
+        v1 = FreeCAD.Vector(5, 5, 20)
+        v2 = FreeCAD.Vector(5.0001, 5, 10)
+        edg = Part.makeLine(v1, v2)
+        args["edge"] = edg
+        self.assertRaises(ValueError, generator.generate, **args)
+
+        # verify linear edge is vertical: Y
+        args = _resetArgs()
+        v1 = FreeCAD.Vector(5, 5.0001, 20)
+        v2 = FreeCAD.Vector(5, 5, 10)
+        edg = Part.makeLine(v1, v2)
+        args["edge"] = edg
+        self.assertRaises(ValueError, generator.generate, **args)
+
+    def test08(self):
+        """Test Helix Generator with horizontal edge"""
+        args = _resetArgs()
+        v1 = FreeCAD.Vector(10, 5, 5)
+        v2 = FreeCAD.Vector(20, 5, 5)
+        edg = Part.makeLine(v1, v2)
+        args["edge"] = edg
+        self.assertRaises(ValueError, generator.generate, **args)
+
+    def test09(self):
+        """Test Helix Generator with inverted vertical edge"""
+        args = _resetArgs()
+        v1 = FreeCAD.Vector(5, 5, 10)
+        v2 = FreeCAD.Vector(5, 5, 20)
+        edg = Part.makeLine(v1, v2)
+        args["edge"] = edg
+
+        result = generator.generate(**args)
+
+        self.assertTrue(type(result) is list)
+        self.assertTrue(type(result[0]) is Path.Command)
+
+        gcode = "".join([r.toGCode() for r in result])
+        self.assertTrue(
+            gcode == self.expectedHelixGCode, "Incorrect helix g-code generated"
+        )