Increased test coverage for internal operations

[termi-official]

Tracking down #67

Reproducer plot

using Ferrite
import FerriteViz
using FerriteViz: ε
import GLMakie #activating the backend, switch to GLMakie or CairoMakie (for 2D) locally

include("src/ferrite-examples/incompressible-elasticity.jl") #defines dh_linear, dh_quadratic, u_linear, u_quadratic and mp

(dh_linear_grad, u_linear_grad) = FerriteViz.interpolate_gradient_field(dh_linear, u_linear, :u)
(dh_quadratic_grad, u_quadratic_grad) = FerriteViz.interpolate_gradient_field(dh_quadratic, u_quadratic, :u)
plotter_linear = FerriteViz.MakiePlotter(dh_linear_grad, u_linear_grad)
plotter_quadratic = FerriteViz.MakiePlotter(dh_quadratic_grad, u_quadratic_grad)
σ(∇u) = 2*mp.G*dev(ε(∇u)) + mp.K*tr(ε(∇u))*ones(ε(∇u)) #helper function to map gradient to stress
cmap = :jet

f = GLMakie.Figure()
axs = [GLMakie.Axis(f[1, 1], title="Strain norm (linear)"),GLMakie.Axis(f[1, 2], title="Stress norm (linear)"),GLMakie.Axis(f[1, 3], title="Pressure (deformed, linear)"),
       GLMakie.Axis(f[3, 1], title="Strain norm (quadratic)"),GLMakie.Axis(f[3, 2], title="Stress norm (quadratic)"),GLMakie.Axis(f[3, 3], title="Pressure (deformed, quadratic)")]
p1 = FerriteViz.solutionplot!(axs[1], plotter_linear, process=∇u->norm(ε(∇u)), colormap=cmap, field=:gradient)
p2 = FerriteViz.solutionplot!(axs[2], plotter_linear, process=∇u->norm(σ(∇u)), colormap=cmap, field=:gradient)
p3 = FerriteViz.solutionplot!(axs[3], dh_linear, u_linear, field=:p, deformation_field=:u, colormap=cmap)
f[2,1] = GLMakie.Colorbar(f[1,1], p1, vertical=false)
f[2,2] = GLMakie.Colorbar(f[1,2], p2, vertical=false)
f[2,3] = GLMakie.Colorbar(f[1,3], p3, vertical=false)

p4 = FerriteViz.solutionplot!(axs[4], plotter_quadratic, process=∇u->norm(ε(∇u)), colormap=cmap, field=:gradient)
p5 = FerriteViz.solutionplot!(axs[5], plotter_quadratic, process=∇u->norm(σ(∇u)), colormap=cmap, field=:gradient)
p6 = FerriteViz.solutionplot!(axs[6], dh_quadratic, u_quadratic, field=:p, deformation_field=:u, colormap=cmap)
f[4,1] = GLMakie.Colorbar(f[3,1], p1, vertical=false)
f[4,2] = GLMakie.Colorbar(f[3,2], p2, vertical=false)
f[4,3] = GLMakie.Colorbar(f[3,3], p3, vertical=false)

f

[koehlerson]

something is broken with the docstring here, cannot mark it in github review

[termi-official]

Yea, I think they never actually worked. Will fix in #106

[termi-official]

Don't mind the branch name.