test(topology): add triangle reference coordinate checks

test/topology/test_triangle_reference_coordinates.jl

@@ -0,0 +1,13 @@
+# SPDX-FileCopyrightText: 2015-2026 Jukka Aho
+# SPDX-License-Identifier: MIT
+
+using Test
+using JuliaFEM
+
+@testset "Triangle reference_coordinates" begin
+    for T in (Triangle{3}, Triangle{6}, Triangle{7}, Triangle{10})
+        rc = reference_coordinates(T())
+        @test length(rc) == nnodes(T())
+        @test rc[1] isa Vec{2,Float64}
+    end
+end