test(basis): add test_type_stability test

Test file included in test/basis/runtests.jl

test/basis/test_type_stability.jl

@@ -0,0 +1,62 @@
+# Test type stability and type parameters
+# Generated functions should work with Float32, Float64, BigFloat, and dual numbers
+using Test
+using StaticArrays, Tensors
+
+include("../../src/topology/api.jl")
+include("../../src/topology/segments.jl")
+include("../../src/topology/triangles.jl")
+include("../../src/topology/quadrilaterals.jl")
+include("../../src/topology/tetrahedra.jl")
+include("../../src/topology/hexahedra.jl")
+include("../../src/topology/pyramids.jl")
+include("../../src/topology/wedges.jl")
+include("../../src/basis/api.jl")
+include("../../src/basis/basis_generated.jl")
+
+@testset "Type Stability" begin
+    @testset "Float64" begin
+        xi = Vec{2,Float64}((0.5, 0.3))
+        N = get_basis_functions(Tri3(), Lagrange{1}(), xi)
+        @test N isa SVector{3,Float64}
+        @test eltype(N) === Float64
+
+        dN = get_basis_derivatives(Tri3(), Lagrange{1}(), xi)
+        @test dN isa SVector{3,Vec{2,Float64}}
+        @test eltype(dN) === Vec{2,Float64}
+    end
+
+    @testset "Float32" begin
+        xi = Vec{2,Float32}((0.5f0, 0.3f0))
+        N = get_basis_functions(Tri3(), Lagrange{1}(), xi)
+        @test N isa SVector{3,Float32}
+        @test eltype(N) === Float32
+
+        dN = get_basis_derivatives(Tri3(), Lagrange{1}(), xi)
+        @test dN isa SVector{3,Vec{2,Float32}}
+        @test eltype(dN) === Vec{2,Float32}
+    end
+
+    @testset "BigFloat" begin
+        xi = Vec{2,BigFloat}((BigFloat("0.5"), BigFloat("0.3")))
+        N = get_basis_functions(Tri3(), Lagrange{1}(), xi)
+        @test N isa SVector{3,BigFloat}
+        @test eltype(N) === BigFloat
+
+        dN = get_basis_derivatives(Tri3(), Lagrange{1}(), xi)
+        @test dN isa SVector{3,Vec{2,BigFloat}}
+        @test eltype(dN) === Vec{2,BigFloat}
+    end
+
+    @testset "3D elements with different types" begin
+        # Test Hex8 with Float32
+        xi32 = Vec{3,Float32}((0.0f0, 0.0f0, 0.0f0))
+        N32 = get_basis_functions(Hex8(), Lagrange{1}(), xi32)
+        @test N32 isa SVector{8,Float32}
+
+        # Test Tet4 with Float64
+        xi64 = Vec{3,Float64}((0.25, 0.25, 0.25))
+        N64 = get_basis_functions(Tet4(), Lagrange{1}(), xi64)
+        @test N64 isa SVector{4,Float64}
+    end
+end