Branch coverage differs between OpenCover and Cobertura

Given the following class being tested and a test of the ConditionalOperator method.
The report generator gives different branch coverage for a report generated from a Cobertura file from Coverlet ( .Net Core version of files below ) to a report generated from an OpenCover file file from OpenCover ( .Net Framework version of the files below ).

public class ToTest
    {
        public string ConditionalOperator(bool isTrue)
        {
            return isTrue ? "True" : "False";
        }
        
    }

public class UnitTest1
    {
        [Fact]
        public void Test1()
        {
            var toTest = new ToTest();
            toTest.ConditionalOperator(true);
        }
    }

66.7% for Net Framework OpenCover , 50% for .NetCore Coverlet

C:\Users\tonyh\AppData\Local\FineCodeCoverage\reportGenerator>reportgenerator -targetdir:C:\Users\tonyh\Downloads\reporter_output  -reports:C:\Users\tonyh\Source\Repos\SUT\Test\bin\Debug\netcoreapp3.1\fine-code-coverage\project.coverage.xml;C:\Users\tonyh\Source\Repos\SUT\UnitTestNetFramework\bin\Debug\fine-code-coverage\project.coverage.xml
2020-12-28T16:17:43: Arguments
2020-12-28T16:17:43:  -targetdir:C:\Users\tonyh\Downloads\reporter_output
2020-12-28T16:17:43:  -reports:C:\Users\tonyh\Source\Repos\SUT\Test\bin\Debug\netcoreapp3.1\fine-code-coverage\project.coverage.xml;C:\Users\tonyh\Source\Repos\SUT\UnitTestNetFramework\bin\Debug\fine-code-coverage\project.coverage.xml
2020-12-28T16:17:43: Writing report file 'C:\Users\tonyh\Downloads\reporter_output\index.html'
2020-12-28T16:17:43: Report generation took 0.3 seconds

Cobertura

<?xml version="1.0" encoding="utf-8"?>
<coverage line-rate="1" branch-rate="0.5" version="1.9" timestamp="1609172247" lines-covered="3" lines-valid="3" branches-covered="1" branches-valid="2">
  <sources>
    <source>C:\</source>
  </sources>
  <packages>
    <package name="SUT" line-rate="1" branch-rate="0.5" complexity="2">
      <classes>
        <class name="SUT.ToTest" filename="Users\tonyh\Source\Repos\SUT\SUT\ToTest.cs" line-rate="1" branch-rate="0.5" complexity="2">
          <methods>
            <method name="ConditionalOperator" signature="(System.Boolean)" line-rate="1" branch-rate="0.5" complexity="2">
              <lines>
                <line number="28" hits="1" branch="False" />
                <line number="29" hits="1" branch="True" condition-coverage="50% (1/2)">
                  <conditions>
                    <condition number="2" type="jump" coverage="50%" />
                  </conditions>
                </line>
                <line number="30" hits="1" branch="False" />
              </lines>
            </method>
          </methods>
          <lines>
            <line number="28" hits="1" branch="False" />
            <line number="29" hits="1" branch="True" condition-coverage="50% (1/2)">
              <conditions>
                <condition number="2" type="jump" coverage="50%" />
              </conditions>
            </line>
            <line number="30" hits="1" branch="False" />
          </lines>
        </class>
      </classes>
    </package>
  </packages>
</coverage>

OpenCover

<?xml version="1.0" encoding="utf-8"?>
<CoverageSession xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" Version="4.7.922.0">
  <Summary numSequencePoints="3" visitedSequencePoints="3" numBranchPoints="3" visitedBranchPoints="2" sequenceCoverage="100" branchCoverage="66.67" maxCyclomaticComplexity="3" minCyclomaticComplexity="1" maxCrapScore="3" minCrapScore="2" visitedClasses="1" numClasses="1" visitedMethods="1" numMethods="1" />
  <Modules>
    <Module hash="5B-E7-52-BD-E0-D0-91-41-A2-A5-8E-5E-07-FD-C6-38-75-C8-9E-69">
      <Summary numSequencePoints="3" visitedSequencePoints="3" numBranchPoints="3" visitedBranchPoints="2" sequenceCoverage="100" branchCoverage="66.67" maxCyclomaticComplexity="3" minCyclomaticComplexity="1" maxCrapScore="3" minCrapScore="2" visitedClasses="1" numClasses="1" visitedMethods="1" numMethods="1" />
      <ModulePath>C:\Users\tonyh\Source\Repos\SUT\UnitTestNetFramework\bin\Debug\SUTNetFramework.dll</ModulePath>
      <ModuleTime>2020-12-28T16:16:17.9590077Z</ModuleTime>
      <ModuleName>SUTNetFramework</ModuleName>
      <Files>
        <File uid="1" fullPath="C:\Users\tonyh\Source\Repos\SUT\SUTNetFramework\Class1.cs" />
      </Files>
      <Classes>
        <Class>
          <Summary numSequencePoints="3" visitedSequencePoints="3" numBranchPoints="3" visitedBranchPoints="2" sequenceCoverage="100" branchCoverage="66.67" maxCyclomaticComplexity="3" minCyclomaticComplexity="1" maxCrapScore="3" minCrapScore="2" visitedClasses="1" numClasses="1" visitedMethods="1" numMethods="1" />
          <FullName>SUTNetFramework.ToTest</FullName>
          <Methods>
            <Method visited="true" cyclomaticComplexity="3" nPathComplexity="2" sequenceCoverage="100" branchCoverage="66.67" crapScore="3" isConstructor="false" isStatic="false" isGetter="false" isSetter="false">
              <Summary numSequencePoints="3" visitedSequencePoints="3" numBranchPoints="3" visitedBranchPoints="2" sequenceCoverage="100" branchCoverage="66.67" maxCyclomaticComplexity="3" minCyclomaticComplexity="3" maxCrapScore="3" minCrapScore="3" visitedClasses="0" numClasses="0" visitedMethods="1" numMethods="1" />
              <MetadataToken>100663297</MetadataToken>
              <Name>System.String SUTNetFramework.ToTest::ConditionalOperator(System.Boolean)</Name>
              <FileRef uid="1" />
              <SequencePoints>
                <SequencePoint vc="1" uspid="1" ordinal="0" offset="0" sl="32" sc="9" el="32" ec="10" bec="0" bev="0" fileid="1" />
                <SequencePoint vc="1" uspid="2" ordinal="1" offset="1" sl="33" sc="13" el="33" ec="46" bec="2" bev="1" fileid="1" />
                <SequencePoint vc="1" uspid="3" ordinal="2" offset="19" sl="34" sc="9" el="34" ec="10" bec="0" bev="0" fileid="1" />
              </SequencePoints>
              <BranchPoints>
                <BranchPoint vc="0" uspid="4" ordinal="0" offset="2" sl="33" path="0" offsetend="4" fileid="1" />
                <BranchPoint vc="1" uspid="5" ordinal="1" offset="2" sl="33" path="1" offsetend="11" fileid="1" />
              </BranchPoints>
              <MethodPoint xsi:type="SequencePoint" vc="1" uspid="1" ordinal="0" offset="0" sl="32" sc="9" el="32" ec="10" bec="0" bev="0" fileid="1" />
            </Method>
            <Method visited="false" cyclomaticComplexity="1" nPathComplexity="0" sequenceCoverage="0" branchCoverage="0" crapScore="2" isConstructor="true" isStatic="false" isGetter="false" isSetter="false">
              <Summary numSequencePoints="0" visitedSequencePoints="0" numBranchPoints="0" visitedBranchPoints="0" sequenceCoverage="0" branchCoverage="0" maxCyclomaticComplexity="1" minCyclomaticComplexity="1" maxCrapScore="2" minCrapScore="2" visitedClasses="0" numClasses="0" visitedMethods="0" numMethods="0" />
              <MetadataToken>100663298</MetadataToken>
              <Name>System.Void SUTNetFramework.ToTest::.ctor()</Name>
              <SequencePoints />
              <BranchPoints />
              <MethodPoint vc="0" uspid="6" ordinal="0" offset="0" />
            </Method>
          </Methods>
        </Class>
      </Classes>
    </Module>
  </Modules>
</CoverageSession>

Despite OpenCover reporting numBranchPoints="3" visitedBranchPoints="2" From https://github.com/danielpalme/ReportGenerator/issues/321#issuecomment-584333807

Only “real” branches ( in OpenCover XML) are taken into account. OpenCover counts differently here, it counts one extra branch per method.

I expect the percentage to be the same for the two report types.

[tonyhallett]

The calculation-details page does not have a visible link on the wiki home page https://github.com/danielpalme/ReportGenerator/wiki

It is there in the collapsed pages section

[danielpalme]

I am surprised that you have not applied your OpenCover “correction/alignment” to the metrics table. Is this a feature that has been requested before ?

All metrics are not 100% accurate if you merge several coverage files. Therefore I decided to show them “as is”. Otherwise I would have to recalculate all of them (which is often not possible without analyzing the source code).