adding TraceFEMTests.jl

[ConnorMallon]

This PR relates relates to solving an equation ( in this case with no derivatives ) on a surface embedded in a volume. TraceFEM is used here for which the space used is the the space of traces of functions in the bulk FESpace on the boundary. Using this method, we can simply used the bulk FESpace restricted to cut cells, integrate along the EmbeddedBoundary and add some term for stability. This seems to work here, but in the new working branch the possibility to restrict a DiscreteModel is gone. The warning says to use a restricted Triangulation - but we cannot define a space based on a Triangulation. What is the alternative here if we want a space which only exists on a surface ?

[codecov-commenter]

Codecov Report

Merging #56 (ee9f10d) into master (86dfcef) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master      #56   +/-   ##
=======================================
  Coverage   87.59%   87.59%           
=======================================
  Files          19       19           
  Lines        1758     1758           
=======================================
  Hits         1540     1540           
  Misses        218      218           

Impacted Files	Coverage Δ
src/Interfaces/EmbeddedDiscretizations.jl	84.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 86dfcef...ee9f10d. Read the comment docs.

[fverdugo]

but we cannot define a space based on a Triangulation.

In release 0.17 will be possible to build a FESpace on a (body fitted) triangulation

[ConnorMallon]

ah ok i see. Probably not the right time for this PR then.

[fverdugo]

We can add it to the current version for the moment. No problem with this.