Adding tests

[codecov[bot]]

Codecov Report

Merging #12 (438518a) into master (831415f) will increase coverage by 74.27%. The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           master      #12       +/-   ##
===========================================
+ Coverage   23.45%   97.72%   +74.27%     
===========================================
  Files          14       15        +1     
  Lines         857     1011      +154     
===========================================
+ Hits          201      988      +787     
+ Misses        656       23      -633     

Impacted Files	Coverage Δ
src/invariant_sets.jl	100.00% <ø> (+100.00%)	:arrow_up:
src/nbody_operators.jl	100.00% <ø> (+94.23%)	:arrow_up:
src/bit_configurations.jl	93.92% <100.00%> (+89.80%)	:arrow_up:
src/common_operators.jl	100.00% <100.00%> (+100.00%)	:arrow_up:
src/compare_vectors.jl	100.00% <100.00%> (ø)
src/equations.jl	100.00% <100.00%> (+100.00%)	:arrow_up:
src/key_tracker.jl	100.00% <100.00%> (ø)
src/multi_configurational_equations.jl	100.00% <100.00%> (+100.00%)	:arrow_up:
src/nbody_matrix_elements.jl	98.30% <100.00%> (+58.30%)	:arrow_up:
src/slater_determinants.jl	96.66% <100.00%> (+85.55%)	:arrow_up:
... and 14 more

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[jagot]

This closes #3.