test calculating features with instances that aren't in data

[rwedge]

This PR adds some tests for the output of calculate_feature_matrix when some of the instances to calculate for aren't in the EntitySet's data

[codecov]

Codecov Report

Merging #559 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #559      +/-   ##
==========================================
+ Coverage   96.31%   96.33%   +0.02%     
==========================================
  Files         115      115              
  Lines        9167     9207      +40     
==========================================
+ Hits         8829     8870      +41     
+ Misses        338      337       -1

Impacted Files	Coverage Δ
...utational_backend/test_calculate_feature_matrix.py	99.35% <100%> (+0.04%)	⬆️
...computational_backends/calculate_feature_matrix.py	98.33% <0%> (+0.41%)	⬆️

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[codecov]

Codecov Report

Merging #559 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #559      +/-   ##
==========================================
+ Coverage   96.33%   96.36%   +0.02%     
==========================================
  Files         116      116              
  Lines        9221     9262      +41     
==========================================
+ Hits         8883     8925      +42     
+ Misses        338      337       -1

Impacted Files	Coverage Δ
...utational_backend/test_calculate_feature_matrix.py	99.35% <100%> (+0.04%)	⬆️
...computational_backends/calculate_feature_matrix.py	98.33% <0%> (+0.41%)	⬆️

---

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Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7dc7d02...28cced3. Read the comment docs.

[CJStadler]

Looks good @rwedge! One optional suggestion.

[CJStadler]

To ensure that these are not in the data (and make it explicit to the reader) you could do something like take the max of the actual ids and then pick 10 higher numbers.