test(fields): add AbstractField API tests

test/fields/test_fields_api.jl

@@ -0,0 +1,32 @@
+# SPDX-FileCopyrightText: 2015-2026 Jukka Aho
+# SPDX-License-Identifier: MIT
+
+using Test
+using JuliaFEM
+
+@testset "fields/api.jl mapping and traits" begin
+    nodes = [10, 20, 30, 40]
+    @testset "Displacement{3}" begin
+        buf = zeros(Int, 12)
+        get_dof_mapping!(buf, Displacement{3}(), nodes)
+        @test buf[1:3] == [28, 29, 30]
+        @test buf[4:6] == [58, 59, 60]
+    end
+    @testset "Temperature & PressurePotential" begin
+        buf = zeros(Int, 4)
+        get_dof_mapping!(buf, Temperature(), nodes)
+        @test buf == nodes
+        get_dof_mapping!(buf, PressurePotential(), nodes)
+        @test buf == nodes
+    end
+    @testset "facet / edge field tags" begin
+        @test dofs_per_node(RT0FaceFlux()) == 1
+        @test dofs_per_node(Nedelec1Edge()) == 1
+        @test quantity_type(RT0FaceFlux) == Float64
+        @test quantity_type(Nedelec1Edge) == Float64
+    end
+    @testset "DisplacementRotation" begin
+        @test dofs_per_node(DisplacementRotation{3}()) == 6
+        @test quantity_type(DisplacementRotation{2}) == Vec{4}
+    end
+end