Instrumenting coverage tool for .net (framework 2.0+ and core) and Mono, reimplemented and extended almost beyond recognition from dot-net-coverage, plus a set of related utilities for processing the results from this and from other programs producing similar output formats.
Start with the Quick Start guide
The latest releases can be downloaded from releases, but the easiest (and most automated) way is through the nuget packages.
For Mono, .net framework and .net core, except as noted
AltCover, a command-line tool for recording code coverage (including dotnet and global tool versions)- MSBuild tasks to drive the tool, including
dotnet testintegration - An API for the above functionality, with Fake and Cake integration
- A PowerShell module for PowerShell 5.1 and PowerShell Core 6+ containing a cmdlet that drives the tool, and other cmdlets for manipulating coverage reports
- A coverage visualizer tool
- For .net framework and mono (for .net framework, needs GTK# v2.12.xx installed separately -- see https://www.mono-project.com/download/stable/#download-win )
- For .net core : needs GTK+3 installed separately -- for Windows, see e.g. https://github.com/GtkSharp/GtkSharp/wiki/Installing-Gtk-on-Windows
General purpose install -- excludes the C# API and FAKE integration
API install -- excludes the .net Framework/mono/GTK#2 Visualizer
dotnet CLI tool install -- excludes the visualizer in all forms
dotnet global tool install -- excludes the visualizer in all forms
Visualizer dotnet global tool -- just the .net core/GTK#3 Visualizer as a global tool
FAKE build task utilities -- just AltCover related helper types for FAKE scripts (v5.18.1 or later), only in this package
As the name suggests, it's an alternative coverage approach. Rather than working by hooking the .net profiling API at run-time, it works by weaving the same sort of extra IL into the assemblies of interest ahead of execution. This means that it should work pretty much everywhere, whatever your platform, so long as the executing process has write access to the results file. You can even mix-and-match between platforms used to instrument and those under test.
In particular, while instrumenting .net core assemblies "just works" with this approach, it also supports Mono, as long as suitable .mdb (or .pdb, in recent versions) symbols are available. One major limitation here is that the .mdb format only stores the start location in the source of any code sequence point, and not the end; consequently any nicely coloured reports that take that information into account may show a bit strangely.
Back in 2010, the new .net version finally removed the deprecated profiling APIs that the free NCover 1.5.x series relied upon. The first version of AltCover was written to both fill a gap in functionality, and to give me an excuse for a ground-up F# project to work on. As such, it saw real production use for about a year and a half, until OpenCover reached a point where it could be used for .net4/x64 work (and I could find time to adapt everything downstream that consumed NCover format input).
Fast forwards to autumn 2017, and I get the chance to dust the project off, with the intention of saying that it worked on Mono, too -- and realise that it's déja vu all over again, because .net core didn't yet have profiler based coverage tools either, and the same approach would work there as well.
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On old-fashioned .net framework, the
ProcessExitevent handling window of ~2s is sufficient for processing significant bodies of code under test (several 10s of kloc, as observed in production back in the '10-'11 timeframe); underdotnet testthevstest.consoleprocess imposes a 100ms guillotine, even though .net Core imposes no time-limit of its own. This is about enough time to fill in an NCover report for a program of no more than 1kloc, hence the development of a "write it all promptly to file and post-process"Runnermode. With version 5.3 and above, thedotnet testintegration now hooks the VSTest in-process data collection, allowing an indefinite window to write collected data from memory, thus removing the file I/O bottleneck. -
Under Mono on non-Windows platforms the default values of
--debug:fullor--debug:pdbonlygenerate no symbols from F# projects -- and without symbols, such assemblies cannot be instrumented. Unlike with C# projects, where the substitution appears to be automatic, to use the necessary--debug:portableoption involves explicitly hand editing the old-school.fsprojfile to have<DebugType>portable</DebugType>.
| Build | AppVeyor   |
Travis  |
| Unit Test coverage | Coveralls  |
See the Wiki page for details
See the current project and long term research items for details; though ad hoc items not in the projects will get added as inspiration or need arise.
All To do and On Hold items are implicitly up for grabs and Help Wanted; most of the current project items are XML manipulation or GUI programming.
I am considering retiring the legacy framework/Mono support after the release of .net 5, contingent on having suitable replacements for Framework-only static analysis tools.
It is assumed that the following are available
.net core SDK 3.1.201 (dotnet) -- try https://www.microsoft.com/net/download
PowerShell Core 7.0.0 or later (pwsh) -- try https://github.com/powershell/powershell
The build may target netstandard2.0 or netcoreapp2.x, but does not need any pre-3.1 runtimes to be installed.
You will need Visual Studio VS2019 (Community Edition) v16.5.3 or later with F# language support (or just the associated build tools and your editor of choice). The NUnit3 Test Runner will simplify the basic in-IDE development cycle. Note that some of the unit tests expect that the separate build of test assemblies under Mono, full .net framework and .net core has taken place; there will be around 20 failures when running the unit tests in Visual Studio from clean when those expected assemblies are not found.
For GTK# support, the GTK# latest 2.12 install is expected -- try https://www.mono-project.com/download/stable/#download-win -- while the latest releases of the GTK#3 libraries will download the native support if the expected version is not detected.
In preparation for the .net 5 unification, on Windows, the default full build uses new-style projects under altcover.core.sln with a few test/helper old-style projects built from MCS.sln; and the build for release only needs these.
It is assumed that mono (version 6.8.x) and dotnet are on the PATH already, and everything is built from the command line, with your favourite editor used for coding.
Start by setting up with dotnet tool restore; this sets up local tools including dotnet fake.
Then dotnet fake run ./Build/setup.fsx to do the rest of the set-up.
Running dotnet fake run ./Build/build.fsx performs a full build/test/package process.
Use dotnet fake run ./Build/build.fsx --target <targetname> to run to a specific target.
If there's a passing build on the CI servers for this commit, then it's likely to be one of the intermittent build failures that can arise from the tooling used. The standard remedy is to try again.
The tests in the AltCover.Test project are ordered in the same dependency order as the code within the AltCover project (the later Runner tests aside). While working on any given layer, it would make sense to comment out all the tests for later files so as to show what is and isn't being covered by explicit testing, rather than merely being cascaded through.
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