Add a reference test

ReferenceTests/src/tests/examples2d.jl

@@ -865,6 +865,32 @@ end
     f
 end
 
+@reference_test "contour 2d with curvilinear grid" begin
+    x = -10:10
+    y = -10:10
+    # The curvilinear grid:
+    xs = [x + 0.01y^3 for x in x, y in y]
+    ys = [y + 10cos(x/40) for x in x, y in y]
+
+    # Now, for simplicity, we calculate the `Z` values to be
+    # the radius from the center of the grid (0, 10).
+    zs = sqrt.(xs .^ 2 .+ (ys .- 10) .^ 2)
+
+
+    # We can use Makie's tick finders to get some nice looking contour levels.
+    # This could also be Makie.get_tickvalues(Makie.LinearTicks(7), extrema(zs)...)
+    # but it's more stable as a test if we hardcode it.
+    levels = 0:4:20
+
+
+    # and now, we plot!
+    fig, ax, srf = surface(xs, ys, zs; shading = NoShading, axis = (; type = Axis, aspect = DataAspect()))
+    ctr = contour!(ax, xs, ys, zs; color = :orange, levels = levels, labels = true, labelfont = :bold, labelsize = 12)
+    translate!(ctr, 0, 0, 10)
+
+    fig
+end
+
 @reference_test "contour labels 3D" begin
     fig = Figure()
     Axis3(fig[1, 1])