minitest-coverage¶ ↑

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Ruby’s contemporary test coverage tools all lie, exaggerating coverage through false-positives and creating a false sense of security; minitest-coverage tries to address this.

Coverage Analysis Tools rely on tracing facilities built into ruby’s VM. You run your tests, and collect data. Seems simple, but that’s a very flawed approach that buffers your coverage numbers up falsely. I’ve witnessed false coverage by as much as 60%, but it could be even worse. Worse, the tracing facilities currently make it impossible to get truly accurate numbers. Even so, they can be improved to be much more accurate.

• Honest test coverage analysis, prone to false negative, not false positive.

• Allows you to record a baseline of your implementation and cache it.

• Allows you to run a subset of your tests with the baseline.

• Allows you to run subsets of your tests and merge them on report.

• Doesn’t require fully mocked tests for accurate coverage analysis.

• Filters results down to the class-under-test to remove false positives.

• FIX: Fails to map some tests back to implementation because of naming mismatches.

• TODO: doesn’t yet integrate with simplecov’s html report system.

• TODO: beta beta beta

• TODO: make fallback code more accurate with manual baseline accounting?

# create baseline in production mode to force load all models & controllers
% minitest_coverage_baseline
% mv coverage.json baseline.json

# run tests in full or in part:
% minitest_coverage --coverage=baseline.json 'test/unit/**/*_test.rb'
% mv coverage.json coverage.unit.json

% minitest_coverage --coverage=baseline.json 'test/{functional,controllers}/**/*_test.rb'
% mv coverage.json coverage.fun.json

# generate a report
% minitest_coverage_report baseline.json coverage.unit.json coverage.fun.json 

uncv  covr% totl : path

 403   4.5%  422 : app/models/option_expense_report/oer_export.rb
 322  11.0%  362 : app/models/certificate_expense.rb
 262   7.4%  283 : app/models/option_expense_report_processor.rb
 237  25.2%  317 : app/controllers/transactions_controller.rb
 209  19.9%  261 : app/models/concerns/excel_sheet.rb
 166  13.1%  191 : app/models/summary_captable.rb
 148  25.3%  198 : app/concerns/formula.rb
 142  10.7%  159 : app/helpers/valuation_reports_helper.rb
 132  33.0%  197 : app/models/public_comp_list.rb
 122  28.7%  171 : app/controllers/permissions_controller.rb
 120  28.1%  167 : lib/importer.rb
 115  36.1%  180 : app/controllers/workflows_controller.rb
 110  46.9%  207 : app/helpers/transactions_helper.rb
 101  35.3%  156 : app/models/ma_comp_list.rb
  97  36.2%  152 : app/models/option_expense_report.rb

[869 lines skipped]

Actual Coverage = 12912 / 24621 = 52.44%

• Ruby, patched currently. :(

• minitest + tests in minitest

• gem install minitest-coverage

This currently requires a patch against ruby to work well. The easiest way to handle this is probably with rbenv+ruby-build or rvm.

The patch SHOULD apply cleanly against 2.3.x, 2.4, and trunk/master.

curl -L http://github.com/ruby/ruby/pull/1456.patch | rbenv install -p 2.4.0-preview1

rvm install 2.4.0-preview1 --patch http://github.com/ruby/ruby/pull/1456.patch

(The MIT License)

Copyright © Ryan Davis, seattle.rb

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