test(topology): add segments test

Test file included in main test/runtests.jl
Tests segment element topology

test/topology/test_segments.jl

@@ -0,0 +1,28 @@
+# This file is a part of JuliaFEM.
+# License is MIT: see https://github.com/JuliaFEM/JuliaFEM.jl/blob/master/LICENSE.md
+
+using JuliaFEM
+using Test
+using StaticArrays
+
+@testset "Segment Elements" begin
+    @testset "Segment{2}" begin
+        @test nnodes(Segment{2}()) == 2
+        @test dim(Segment{2}()) == 1
+        @test nvertices(Segment{2}()) == 2
+        @test nedges(Segment{2}()) == 1
+        @test nfaces(Segment{2}()) == 2  # Endpoints
+        
+        # Entity queries
+        @test nentities(Segment{2}, Vertex) == 2
+        @test nentities(Segment{2}, Edge) == 1
+        @test nentities(Segment{2}, Cell) == 1
+    end
+    
+    @testset "Segment{3}" begin
+        @test nnodes(Segment{3}()) == 3
+        @test nvertices(Segment{3}()) == 2  # Same topology as Segment{2}
+        @test nedges(Segment{3}()) == 1
+        @test nentities(Segment{3}, Edge) == 1
+    end
+end