coverage-report

name	coverage-report
description	Rake task for analyzing test coverage from coverage/coverage.json. Group by directory, filter by pattern, check git diff coverage, shows uncovered line numbers.

Coverage Report Rake Task

After running tests with SimpleCov (JSON formatter enabled), use rails coverage:report to analyze results.

Prerequisites

Tests must be run first to generate coverage/coverage.json:

bundle exec rspec

If the JSON file is missing, the task will abort with instructions to run tests.

Commands

Full report — all files grouped by directory

rails coverage:report

Filter by file name / pattern (regex)

rails 'coverage:report[worst,order]'
rails 'coverage:report[worst,payment_provider]'
rails 'coverage:report[worst,controllers/.*_controller]'

Git diff modes — coverage of changed lines only

rails 'coverage:report[worst,,staged]'      # staged changes only
rails 'coverage:report[worst,,unstaged]'    # unstaged changes only
rails 'coverage:report[worst,,head]'        # last commit (HEAD~1..HEAD)
rails 'coverage:report[worst,,branch]'      # all changes since branching from main/master

Git mode parses git diff output and shows coverage only for the lines you actually changed. Files without changed lines in app/ are excluded. Uncovered line numbers shown are intersected with the diff — only changed lines that lack test coverage are listed.

Sort modes

rails 'coverage:report[worst]'        # all files sorted worst-first (default)
rails 'coverage:report[uncovered]'    # only 0% coverage files
rails 'coverage:report[partial]'      # only partially covered (1-99%)
rails 'coverage:report[full]'         # only 100% covered files

Combine filter + sort

rails 'coverage:report[uncovered,service]'
rails 'coverage:report[partial,admin]'

Combine filter + git

rails 'coverage:report[worst,order,staged]'

Output Format

============================================================
  Coverage Report [filter: service]
  397/447 lines (88.81%)
============================================================

--- app/services (88.8% | 397/447) ---
   81.8%  app/services/asset_purchase_service.rb  (4 missed of 22)
         uncovered: 26-27, 40-41
   83.3%  app/services/tournament_resolution_service.rb  (6 missed of 36)
         uncovered: 19, 35, 66-67, 85-86
   90.7%  app/services/order_completion_service.rb  (5 missed of 54)
         uncovered: 39-40, 53-54, 125
  100.0%  app/services/order_builder.rb  (0 missed of 12)

Each group shows: directory name, group coverage %, covered/total lines. Each file shows: coverage %, path, missed lines count, total relevant lines, and uncovered line ranges.

Consecutive uncovered lines are collapsed into ranges (26-27 instead of 26, 27).

In git mode, files are tagged with [changed] and stats reflect only changed lines. The uncovered: line shows only those changed lines that are not covered by tests — this is the primary signal for what needs test attention.

Groups

Files are automatically grouped into:

• app/controllers, app/models, app/services, app/helpers
• app/jobs, app/mailers, app/queries, app/channels
• app/concerns, app/views
• app/other — anything else under app/ (admin, configs, etc.)

When to Use

• After implementing a feature + tests: rails coverage:report[worst,,staged] to verify changed lines are covered — uncovered line numbers point directly to gaps.
• After a PR is ready: rails coverage:report[worst,,branch] to review coverage of all branch changes.
• Exploring weak spots: rails coverage:report[partial] to find partially covered files with specific line numbers to target.
• Checking specific area: rails 'coverage:report[partial,payment]' to focus on a domain.
• Finding dead code: rails coverage:report[uncovered] to find completely untested files.