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.NET Learning Notes: How to View Code Coverage in .NET Projects(with Coverlet + Reportgenerator)

Measuring test coverage is crucial for understanding how much of your codebase is actually being tested. This blog walks you through how to generate code coverage reports, convert them into human-friendly HTML, and explains the difference between Line Coverage and Branch Coverage.

Step 1: Add Necessary Packages

In your test project .csproj file, ensure the following packages are installed:

<PackageReference Include="coverlet.collector" Version="6.0.2" />
<PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
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You can install via CLI:

dotnet add package coverlet.collector
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Step 2: Run Tests with Coverage Collection

Use the dotnet test command with coverage parameters:

dotnet test \
  --collect:"XPlat Code Coverage"
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This will generate a file like:

TestResults/{guid}/coverage.cobertura.xml
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This .xml file is in Cobertura format, and we’ll use it to generate a readable report.

Step 3: Install ReportGenerator (if not already) 

dotnet tool install -g dotnet-reportgenerator-globaltool
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If it’s already installed and can’t be found, make sure you export the tool path:

export PATH="$PATH:$HOME/.dotnet/tools"
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Step 4: Generate HTML Report

Use the following command in your test project:

reportgenerator \
  -reports:"TestResults/**/coverage.cobertura.xml" \
  -targetdir:"coverage-report" \
  -reporttypes:Html
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You’ll now find an index.html file inside the coverage-report folder. Open it in a browser to view detailed coverage.

Line Coverage vs Branch Coverage

Here’s a quick summary:

Metric Description Example
Line Coverage Has each line of code been executed? if (x > 0) ran once → counted as covered
Branch Coverage Has each logical path (true/false) of conditionals been run? Must test both x > 0 and x <= 0

Branch coverage helps you detect untested logic paths, while line coverage only tells you whether the line ran or not.

My Report Screenshot

Coverage Overview

Detailed Coverage in Each Class

Excluding Files or Classes from Code Coverage

Sometimes, you may want to exclude specific files, classes, or folders from code coverage—for example, DbContext, auto-generated migrations, or testing helpers. You can configure these exclusions using a .runsettings file.

1. Create a coverlet.runsettings File

Place this file at the root of your project or solution (or anywhere but you need to specify the location in your command):

<RunSettings>
  <DataCollectionRunSettings>
    <DataCollectors>
      <DataCollector friendlyName="XPlat code coverage">
        <Configuration>
          <Exclude>
            <!-- Exclude specific class names or folders -->
            <ModulePath>.*Tests.*</ModulePath>
            <ClassName>.*DbContext.*</ClassName>
            <ClassName>.*Migrations.*</ClassName>
            <ClassName>.*FakeService.*</ClassName>
          </Exclude>
        </Configuration>
      </DataCollector>
    </DataCollectors>
  </DataCollectionRunSettings>
</RunSettings>
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2. Use the File in Your Coverage Command

Tell the test runner to use this settings file:

dotnet test --settings coverlet.runsettings
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This will exclude the specified classes or paths from the final coverage result.

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