[test] add test for mergemesh

Author: fangq

README.md

@@ -276,14 +276,14 @@ tracked in https://github.com/NeuroJSON/pyiso2mesh/issues/1
 | ✅ `remeshsurf.m` | ✅ tested |
 | ✅ `smoothsurf.m` | ✅ tested |
 | ✅ `sortmesh.m` | ⭕️ tested |
-| ✅ `mergemesh.m` | ⭕️ tested |
+| ✅ `mergemesh.m` | ✅ tested |
 | ✅ `meshrefine.m` | ✅ tested |
 | ✅ `mergesurf.m` | ⭕️ tested |
 | ✅ `surfboolean.m` | ✅ tested |
 | ✅ `fillsurf.m` | ⭕️ tested |
-| ✅ `highordertet.m` | ⭕️ tested |
-| ✅ `elemfacecenter.m` | ⭕️ tested |
-| ✅ `barydualmesh.m` | ⭕️ tested |
+| ✅ `highordertet.m` | ✅ tested |
+| ✅ `elemfacecenter.m` | ✅ tested |
+| ✅ `barydualmesh.m` | ✅ tested |
 | ✅ `meshinterp.m` | ⭕️ tested |
 | ✅ `meshremap.m` | ⭕️ tested |
 | ✅ `extrudesurf.m` | ⭕️ tested |

test/run_test.py

@@ -1055,6 +1055,14 @@ def test_surfboolean_self(self):
             surfboolean(self.no1, self.el1, "self", self.no2, self.el2)[0], 1
         )
 
+    def test_mergemesh(self):
+        no1, fc1 = mergemesh(self.no1, self.el1, self.no2, self.el2)
+        self.assertEqual(no1.shape[0], self.no1.shape[0] + self.no2.shape[0])
+        self.assertEqual(no1.shape[0], np.max(fc1))
+        no1, fc1 = mergemesh(self.no1, self.el1, self.no2, self.el2, self.no1, self.el1)
+        self.assertEqual(no1.shape[0], 2 * self.no1.shape[0] + self.no2.shape[0])
+        self.assertEqual(no1.shape[0], np.max(fc1))
+
 
 class Test_core(unittest.TestCase):
     def __init__(self, *args, **kwargs):