Improve test coverage & fix discovered bugs

[xsc]

Based on the codecov.io report, increases test coverage for namespaces that are currently not tested at all.

[codecov-io]

Codecov Report

Merging #16 into master will increase coverage by 12.11%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           master      #16       +/-   ##
===========================================
+ Coverage    78.2%   90.32%   +12.11%     
===========================================
  Files          60       60               
  Lines        1652     1581       -71     
  Branches       50       52        +2     
===========================================
+ Hits         1292     1428      +136     
+ Misses        310      102      -208     
- Partials       50       51        +1

Impacted Files	Coverage Δ
src/claro/projection/level.cljc	77.77% <100%> (+36.11%)	⬆️
src/claro/projection/juxt.cljc	100% <100%> (+17.64%)	⬆️
src/claro/data/error.cljc	94.28% <100%> (+17.14%)	⬆️
src/claro/projection/union.cljc	92.06% <100%> (+9.45%)	⬆️
src/claro/projection/conditional.cljc	100% <100%> (ø)	⬆️
src/claro/projection/parameters.cljc	68.42% <100%> (+13.03%)	⬆️
src/claro/projection/maps.cljc	96.66% <100%> (-0.11%)	⬇️
src/claro/projection/value.cljc	100% <100%> (+44%)	⬆️
src/claro/projection/objects.cljc	100% <100%> (+8.33%)	⬆️
src/claro/projection/remove_nil.clj	92% <100%> (+67%)	⬆️
... and 28 more

---

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 aa13cc4...d56f45c. Read the comment docs.