coverage-report

/dotnet:coverage-report

Generate comprehensive test coverage reports with HTML visualization, threshold enforcement, and coverage gap analysis.

Arguments

Parse arguments from $ARGUMENTS:

Flag	Description	Default
--format <format>	Output format (cobertura, opencover, html, all)	html
--threshold <percent>	Fail if line coverage below threshold	None
--project <path>	Target specific test project	All test projects
--output <path>	Output directory for reports	./coverage
--open	Open HTML report in browser	false
--history	Include historical trends (if available)	false

Prerequisites

This command requires coverage tools. If not installed, will prompt:

Coverage tools not found. Install now?

Required:
  - dotnet-coverage (collection)
  - reportgenerator (HTML reports)

Run: /dotnet:install-tool --tool coverage
Run: /dotnet:install-tool --tool reportgen --global

Workflow

Step 1: Check Tool Availability

# Check for coverage tools
dotnet tool list | grep -E "dotnet-coverage|reportgenerator"

# Check global tools
dotnet tool list --global | grep reportgenerator

If missing, offer to install via /dotnet:install-tool.

Step 2: Find Test Projects

# Find test projects by convention
find . -name "*.Tests.csproj" -o -name "*.Test.csproj" -o -name "*Tests.csproj"

# Or by reference to test frameworks
grep -l "Microsoft.NET.Test.Sdk" **/*.csproj

Step 3: Run Tests with Coverage

Using dotnet-coverage (recommended for .NET 6+):

dotnet-coverage collect \
  --output coverage.cobertura.xml \
  --output-format cobertura \
  dotnet test --no-build

Using coverlet (alternative):

dotnet test \
  --collect:"XPlat Code Coverage" \
  --results-directory ./coverage

Step 4: Generate HTML Report

reportgenerator \
  -reports:coverage.cobertura.xml \
  -targetdir:./coverage/html \
  -reporttypes:Html \
  -assemblyfilters:"-*.Tests;-*.Test" \
  -classfilters:"-*Migrations*"

Step 5: Analyze Coverage

Parse coverage report for metrics:

• Line coverage percentage
• Branch coverage percentage
• Method coverage percentage
• Uncovered lines by file

Step 6: Threshold Check

If --threshold specified:

Coverage threshold check:
  Required: 80%
  Actual: 72.5%

  Status: FAILED

  Files below threshold:
    - src/MyApp/Services/PaymentService.cs (45%)
    - src/MyApp/Handlers/OrderHandler.cs (52%)
    - src/MyApp/Controllers/ReportController.cs (61%)

Output Format

Summary Report:

Test Coverage Report

Generated: 2026-01-18 11:00:00 UTC
Test Projects: 3
Tests Run: 247 passed, 0 failed

═══════════════════════════════════════════════════════════════
                    COVERAGE SUMMARY
═══════════════════════════════════════════════════════════════

  Metric              Coverage    Target    Status
  ─────────────────────────────────────────────────
  Line Coverage       78.5%       80%       WARN
  Branch Coverage     65.2%       70%       WARN
  Method Coverage     85.3%       80%       PASS

═══════════════════════════════════════════════════════════════

Coverage by Project:
  Project                    Lines      Branches   Methods
  ─────────────────────────────────────────────────────────
  MyApp.Core                 92.1%      88.5%      95.0%
  MyApp.Api                  75.3%      62.1%      82.4%
  MyApp.Infrastructure       68.2%      55.0%      78.6%

Top Uncovered Files:
  File                                    Coverage  Uncovered
  ────────────────────────────────────────────────────────────
  Services/PaymentService.cs              45.2%     87 lines
  Handlers/OrderHandler.cs                52.1%     64 lines
  Controllers/ReportController.cs         61.8%     45 lines
  Repositories/AuditRepository.cs         64.5%     38 lines
  Services/NotificationService.cs         67.2%     31 lines

Coverage Gaps (uncovered code patterns):
  - Exception handlers: 23 catch blocks untested
  - Edge cases: 15 null checks untested
  - Error paths: 12 error branches untested

HTML Report: ./coverage/html/index.html

Detailed Per-File Report:

Coverage Details: src/MyApp/Services/PaymentService.cs

  Overall: 45.2% (78/172 lines covered)

  Covered Methods:
    ✓ ProcessPayment()         100% (15/15 lines)
    ✓ ValidateCard()           100% (12/12 lines)
    ✓ GetPaymentStatus()       95%  (19/20 lines)

  Partially Covered Methods:
    ~ RefundPayment()          42%  (8/19 lines)
    ~ HandleFailure()          35%  (7/20 lines)

  Uncovered Methods:
    ✗ RetryPayment()           0%   (0/25 lines)
    ✗ ProcessBatchPayments()   0%   (0/31 lines)
    ✗ HandleWebhook()          0%   (0/30 lines)

  Uncovered Line Ranges:
    Lines 145-169: RetryPayment() - retry logic
    Lines 180-210: ProcessBatchPayments() - batch processing
    Lines 220-249: HandleWebhook() - webhook handling

  Recommendations:
    1. Add tests for retry scenarios
    2. Add tests for batch payment edge cases
    3. Add tests for webhook validation

Threshold Failure:

COVERAGE THRESHOLD FAILED

  Required: 80% line coverage
  Actual: 72.5% line coverage
  Gap: 7.5%

  To reach 80% coverage, add tests for ~150 more lines

  Quick wins (highest impact):
    1. PaymentService.cs: +27 lines = +1.5%
    2. OrderHandler.cs: +24 lines = +1.3%
    3. ReportController.cs: +18 lines = +1.0%

  Exit code: 1 (threshold not met)

Report Formats

Format	Description	Use Case
cobertura	XML format	CI/CD integration, Azure DevOps
opencover	XML format	SonarQube, older tools
html	Interactive HTML	Local review, PR reviews
lcov	LCOV format	GitHub Actions, Codecov
all	Generate all formats	Comprehensive reporting

Integration Examples

Azure DevOps:

- task: PublishCodeCoverageResults@1
  inputs:
    codeCoverageTool: Cobertura
    summaryFileLocation: '$(Build.SourcesDirectory)/coverage/coverage.cobertura.xml'

GitHub Actions:

- name: Upload coverage to Codecov
  uses: codecov/codecov-action@v3
  with:
    files: ./coverage/coverage.cobertura.xml

SonarQube:

dotnet sonarscanner begin \
  /k:"project-key" \
  /d:sonar.cs.opencover.reportsPaths="coverage/coverage.opencover.xml"

Examples

# Generate HTML coverage report
/dotnet:coverage-report

# Generate report with threshold enforcement
/dotnet:coverage-report --threshold 80

# Generate Cobertura XML for CI
/dotnet:coverage-report --format cobertura

# Generate all formats
/dotnet:coverage-report --format all

# Target specific test project
/dotnet:coverage-report --project MyApp.Tests

# Open report in browser
/dotnet:coverage-report --open

# Custom output directory
/dotnet:coverage-report --output ./artifacts/coverage

Filtering

Exclude from coverage analysis:

• Test projects (*.Tests, *.Test)
• Generated code (Migrations, designer files)
• Third-party code

Configure in reportgenerator call:

-assemblyfilters:"-*.Tests;-*.Test;-*.Migrations"
-classfilters:"-*Generated*;-*Designer*"

Historical Trends

If --history and previous reports exist:

Coverage Trend (last 5 runs):

  Date          Line%   Branch%   Change
  ──────────────────────────────────────
  2026-01-18    78.5%   65.2%     +2.1%
  2026-01-15    76.4%   63.8%     +1.5%
  2026-01-12    74.9%   62.1%     +0.8%
  2026-01-10    74.1%   61.5%     -0.5%
  2026-01-08    74.6%   62.0%     --

  Trend: Improving (+3.9% over 10 days)