FEM: constraint tie, add input file writing unit test

src/Mod/Fem/CMakeLists.txt

@@ -173,6 +173,7 @@ SET(FemTestsCcx_SRCS
     femtest/data/ccx/constraint_contact_shell_shell.inp
     femtest/data/ccx/constraint_contact_solid_solid.FCStd
     femtest/data/ccx/constraint_contact_solid_solid.inp
+    femtest/data/ccx/constraint_tie.inp
     femtest/data/ccx/cube_frequency.inp
     femtest/data/ccx/cube_frequency.dat
     femtest/data/ccx/cube_frequency.frd

src/Mod/Fem/TestFem.py

@@ -127,6 +127,7 @@ gf()
 ./bin/FreeCADCmd --run-test "femtest.app.test_ccxtools.TestCcxTools.test_static_analysis"
 ./bin/FreeCADCmd --run-test "femtest.app.test_ccxtools.TestCcxTools.test_static_constraint_contact_shell_shell"
 ./bin/FreeCADCmd --run-test "femtest.app.test_ccxtools.TestCcxTools.test_static_constraint_contact_solid_solid"
+./bin/FreeCADCmd --run-test "femtest.app.test_ccxtools.TestCcxTools.test_static_constraint_tie"
 ./bin/FreeCADCmd --run-test "femtest.app.test_ccxtools.TestCcxTools.test_static_material_multiple"
 ./bin/FreeCADCmd --run-test "femtest.app.test_ccxtools.TestCcxTools.test_static_material_nonlinar"
 ./bin/FreeCADCmd --run-test "femtest.app.test_ccxtools.TestCcxTools.test_thermomech_bimetall"
@@ -178,6 +179,9 @@ unittest.TextTestRunner().run(unittest.TestLoader().loadTestsFromName("femtest.a
 import unittest
 unittest.TextTestRunner().run(unittest.TestLoader().loadTestsFromName("femtest.app.test_ccxtools.TestCcxTools.test_static_constraint_contact_solid_solid"))
 
+import unittest
+unittest.TextTestRunner().run(unittest.TestLoader().loadTestsFromName("femtest.app.test_ccxtools.TestCcxTools.test_static_constraint_tie"))
+
 import unittest
 unittest.TextTestRunner().run(unittest.TestLoader().loadTestsFromName("femtest.app.test_ccxtools.TestCcxTools.test_static_material_multiple"))
 

src/Mod/Fem/femtest/app/test_ccxtools.py

@@ -176,6 +176,27 @@ class TestCcxTools(unittest.TestCase):
         )
         """
 
+    # ********************************************************************************************
+    def test_static_constraint_tie(
+        self
+    ):
+        # set up
+        from femexamples.constraint_tie import setup
+        setup(self.active_doc, "ccxtools")
+        test_name = "constraint tie"
+        base_name = "constraint_tie"
+        analysis_dir = testtools.get_unit_test_tmp_dir(
+            self.temp_dir,
+            "FEM_ccx_constraint_tie",
+        )
+
+        # test input file writing
+        self.input_file_writing_test(
+            test_name=test_name,
+            base_name=base_name,
+            analysis_dir=analysis_dir,
+        )
+
     # ********************************************************************************************
     def test_static_material_multiple(
         self