NCover FAQ

If you have questions that this document does not address, contact Peter Waldschmidt or try the NCover Forums.

1. What is code coverage analysis?

A code coverage analyzer monitors your code at runtime and records information about which lines of code were executed. NCover shows each sequence point in your application along with the number of times that point was executed. Sequence points are generated by the compiler and stored in the debug information (.pdb) files. A sequence point basically corresponds to a single program statement (often a line of code) in your high-level language.

2. Why would I want to do code coverage analysis?

Unit test suites are often used as a quality tool during the development process to keep the codebase stable as it changes and expands. Tools such as NUnit are often used to run and report on the test suites. However, when implementing unit testing in your build process, you have no way of knowing how much of your code the unit tests are actually testing. This is where code coverage comes in. You can run NUnit within NCover and use the code coverage report to determine which code was not tested by that particular test suite.

3. What versions of the CLR does NCover support?

NCover 1.5.x requires the .NET framework version 2.0.50727 to be installed; however, the application being profiled can be written against any shipping version of the framework. NCover has been tested profiling coverage of .NET 2.0, .NET 1.1 and .NET 1.0 applications.

4. Which version of NCover should I install?

If you have the .NET 2.0 framework installed on your machine then you should use the latest NCover version available. NCover as of version 1.5 can profile .NET 2.0, 1.1 and 1.0 applications.

For development teams who do not have the .NET framework 2.0 installed but do have the .NET framework version 1.1.4322, you can try NCover 1.3.3. Note however that this version is no longer supported as it has a number of known issues and limitations.

5. What is the command line syntax for NCover?

Here is the usage info from the NCover command line (for NCover versions from 1.5.6 only):

NCover.Console [<command line> [<command args>]]
               [//svc <service name>]
               [//a <assembly list>]
               [//w <working directory>]
               [//ea <exclusion list>]
               [//x <xml output file>]
               [//s [<settings file>]] [//r [<settings file>]]
               [//v] [//q] 
               [//l <log file>]

//svc  For profiling windows services
//iis  For profiling web applications

//a    List of assemblies to profile separated by semi-colons i.e. "MyAssembly1;MyAssembly2". Do not include paths or suffixes.
//w    Working directory for profiled application 
//ea   List of attributes marking classes or methods to exclude from coverage 

//reg  Register profiler temporarily for user. (helps with xcopy deployment) 
//x    Specify coverage output file. (default: coverage.xml).

//s    Save settings to a file (defaults: NCover.Settings) 
//r    Use settings file, overriding other settings (default: NCover.Settings) 

//l    Specify profiler log file (default: coverage.log).
//q    No logging (quiet) 
//v    Enable verbose logging (show instrumented code)

6. Does NCover required a special compilation step for my code?

No. Some code coverage tools change your source code and force you to recompile it into a special build.  NCover is designed to work on shipping code.  NCover uses the .NET Framework profiling API to monitor your code. It does require build symbols, but can be run on release code without any modifications.

7. How does NCover work?

NCover uses the .NET Framework profiler API to monitor an application's execution. When a method is loaded by the CLR, NCover retrieves the IL and replaces it with instrumented IL code.  NCover does not change your original IL code, it simply inserts new code to update a visit counter at each sequence point.  Upon request, (usually after the .NET process has shut down) the profiler outputs statistics to the coverage file.

8. What is the output of NCover?

NCover generally writes out three files after analysis completes.

Example XML output
<method class="NCoverTest.ClassLoaded" name="HasDeadCode">
    <seqpnt document="C:\Dev\Utilities\ncover\NCoverTest\NCoverTest.cs"
            column="13" line="48" endcolumn="58" endline="48" visitcount="1" /> 
    <seqpnt document="C:\Dev\Utilities\ncover\NCoverTest\NCoverTest.cs" 
            column="13" line="49" endcolumn="22" endline="49" visitcount="1" /> 
    <seqpnt document="C:\Dev\Utilities\ncover\NCoverTest\NCoverTest.cs" 
            column="17" line="50" endcolumn="24" endline="50" visitcount="1" /> 
    <seqpnt document="C:\Dev\Utilities\ncover\NCoverTest\NCoverTest.cs" 
            column="13" line="51" endcolumn="48" endline="51" visitcount="0" /> 
    <seqpnt document="C:\Dev\Utilities\ncover\NCoverTest\NCoverTest.cs" 
            column="9" line="52"  endcolumn="10" endline="52" visitcount="0" /> 

Example transformed output
Visit Count Line Column End Line End Column Document
1 48 13 48 58 C:\Dev\Utilities\ncover\NCoverTest\NCoverTest.cs
1 49 13 49 22 C:\Dev\Utilities\ncover\NCoverTest\NCoverTest.cs
1 50 17 50 24 C:\Dev\Utilities\ncover\NCoverTest\NCoverTest.cs
0 51 13 51 48 C:\Dev\Utilities\ncover\NCoverTest\NCoverTest.cs
0 52 9 52 10 C:\Dev\Utilities\ncover\NCoverTest\NCoverTest.cs

Suggested usages of the coverage.xml output are to display it in the NCoverExplorer gui with the source code highlighted, to generate html reports, or to include it in your continuous build server reports such as CruiseControl.Net. For more information on these options see below in the FAQ.

9. How do I use coverage exclusions?

First you should define an attribute to markup your excluded code with. You will likely want to put this in a common assembly to make it reusable, or indeed within a "CommonAssemblyInfo.cs" that you include in all your application assemblies.

namespace MyNamespace {
    class CoverageExcludeAttribute : System.Attribute { }

Apply the attribute to the C# classes and/or methods you wish to mark as excluded from code coverage statistics:

    private void SomeMethodToExclude() {}    

Finally, ensure you pass the full qualified attribute information in the NCover command line:

    NCover.Console MyApplication.exe //ea MyNamespace.CoverageExcludeAttribute    

Note that if you are using the TestDriven.Net VS.Net add-in to "Test with Coverage" it will automatically pass through "//ea CoverageExcludeAttribute" which you should define without a namespace like above. For further information refer to this blog entry.

10. Examples

Coverage while running a simple executable until it exits:

    NCover.Console MyApplication.exe

Coverage while running all the unit tests in an assembly using NUnit, profiling all loaded assemblies with .pdb build symbols:

    NCover.Console nunit-console.exe MyApplication.Tests.dll

Coverage of only a subset of loaded assemblies while running unit tests:

    NCover.Console nunit-console.exe MyApplication.Tests.dll //a MyApplication.Core;MyApplication.Utilities

Coverage of a windows service. Stop the service to generate the coverage output:

    NCover.Console //svc MyServiceName

Coverage of an ASP.Net application. Stop the IIS service to generate the coverage output:

    NCover.Console //iis

11. Where can I get help or support?

Your best approach is to browse the NCover forums as well as the blog by the author Peter Waldschmidt. If you cannot find a similar issue mentioned feel free to post your query and perhaps someone can help.

12. How do I "xcopy deploy" NCover like my other build tools?

Many developers prefer to have their build tools such as NUnit, NAnt etc stored in source control in a Tools folder along with the source code. This ensures that a new developer can obtain and build the application without having to install additional tools on their own machines.

NCover can also be deployed in this fashion. However the one gotcha with NCover versus other tools is that the profiler within CoverLib.dll must be COM registered on the local machine before you execute it. Prior to NCover 1.5.6 this was usually achieved as part of your build script, which would call regsvr32 with the path to the CoverLib.dll in your Tools folder. Alternatively the <ncover> NAnt and MSBuild tasks described below will do this for you. As of NCover 1.5.6 you can also use the //reg option in the command line arguments which will temporarily register the profiler. Note that the //reg option will not work for IIS or Windows Service profiling unless you are running NCover under the same Windows login account as the IIS worker process, or your Windows Service.

13. How do I see my source code highlighted with the coverage results?

NCoverExplorer is a gui and console-based .NET application developed by Grant Drake. NCoverExplorer parses the coverage.xml files output from NCover and displays the results integrated with your source code. It also includes a number of additional features to merge, filter, sort and generate html reports. The console version is designed to be used as part of an automated build process. The support forums for NCoverExplorer are located with the NCover ones at 

14. How do I run NCover from within the Visual Studio.Net IDE?

The TestDriven.Net add-in by Jamie Cansdale offers a right-click capability within the IDE to execute your unit tests with code coverage. The results of the NCover code coverage are displayed with the bundled NCoverExplorer gui for analysis and reporting.

15. How do I run NCover from a NAnt or MSBuild task?

You can use an <exec> task with NAnt or an <Exec> task with MSBuild. Alternatively you may want to use the custom <ncover> task for NAnt or <NCover> task for MSBuild developed by Grant Drake for a more developer friendly syntax. The source code, compiled assemblies and documentation are located in the available from

16. How do I include NCover output in my CruiseControl.Net build reports?

CruiseControl.Net is a continuous integration build server which offers web-based reporting of the outputs of a build such as unit test results and code coverage reporting. The default CruiseControl.Net installation includes a basic stylesheet which works in combination with the standard coverage.xml formatted output. So all you need to do is include the execution of NCover as part of your build, then add a CruiseControl.Net merge file publisher task to integrate the coverage.xml results into the build output.

An improvement on the above to display more attractive and powerful reports as well as minimize the build log size is to use NCoverExplorer. The NCoverExplorer.Console.exe is designed to produce a more concise xml report summary that is combined with an alternate xsl stylesheet for CruiseControl.Net. You can find more information and screenshots in this blog entry - all the necessary tasks, examples and documentation are located within available from

17. How do I merge multiple NCover coverage.xml results?

You can can use NCoverExplorer to merge the results of multiple coverage runs. For more information refer to this blog entry.

18. Troubleshooting: Why is my coverage.xml file empty?

19. Troubleshooting: I have coverage.xml output but my XYZ assembly is not included in it?

20. Troubleshooting: After running NCover my coverage.log says "Failed to load symbols for module XYZ"?

21. Troubleshooting: I get a "Profiled process terminated. Profiler connection not established" message?

22. Troubleshooting: My coverage exclusions are not working?