Can I write into the console in a unit test If yes why doesn t the console window open

Question

I have a test project in Visual Studio  I use Microsoft VisualStudio TestTools UnitTesting  I add this line in one of my unit tests  Console WriteLine  quot Some foo was very angry with boo quot    Console ReadLine     When I run the test  the test passes  but the console window is not opened at all  Is there a way to make the console window available to be interacted via a unit test

User · Answer

There are several ways to write output from a Visual Studio unit test in C#:

Console.Write - The Visual Studio test harness will capture this and show it when you select the test in the Test Explorer and click the Output link. Does not show up in the Visual Studio Output Window when either running or debugging a unit test (arguably this is a bug).
Debug.Write - The Visual Studio test harness will capture this and show it in the test output. Does appear in the Visual Studio Output Window when debugging a unit test, unless Visual Studio Debugging options are configured to redirect Output to the Immediate Window. Nothing will appear in the Output (or Immediate) Window if you simply run the test without debugging. By default only available in a Debug build (that is, when DEBUG constant is defined).
Trace.Write - The Visual Studio test harness will capture this and show it in the test output. Does appear in the Visual Studio Output (or Immediate) Window when debugging a unit test (but not when simply running the test without debugging). By default available in both Debug and Release builds (that is, when TRACE constant is defined).

Confirmed in Visual Studio 2013 Professional.

User · Answer

You could use this line to write to Output Window of the Visual Studio  System Diagnostics Debug WriteLine  quot Matrix has you    quot     Must run in Debug mode

User · Answer

Visual Studio For Mac None of the other solutions worked on Visual  Studio for Mac If you are using NUnit  you can add a small  NET Console Project to your solution  and then reference the project you wish to test in the References of that new Console Project  Whatever you were doing in your  Test    methods can be done in the Main of the console application in this fashion  class MainClass       public static void Main string   args                Console WriteLine  quot Console quot                Reproduce the unit test         var classToTest   new ClassToTest            var expected   42          var actual   classToTest MeaningOfLife            Console WriteLine   quot Pass   expected Equals actual    expected  expected   actual  actual  quot              You are free to use Console Write and Console WriteLine in your code under these circumstances

User · Answer

IMHO  output messages are relevant only for failed test cases in most cases  I made up the below format  and you can make your own too  This is displayed in the Visual  Studio Test Explorer Window itself  How can we throw this message in the Visual  Studio Test Explorer Window  Sample code like this should work  if test condition fails      Assert Fail   quot Test Type  Positive Negative                  Mock Properties  someclass propertyOne  True                 someclass propertyTwo  True                 Test Properties  someclass testPropertyOne  True                 someclass testPropertyOne  False                 Reason for Failure  The Mail was not sent on Success Task completion  quot     You can have a separate class dedicated to this for you

User · Answer

In Visual  Studio  2017   quot TestContext quot  doesn t show the Output link into Test Explorer  However  Trace Writeline   shows the Output link

User · Answer

First of all unit tests are  by design  supposed to run completely without interaction   With that aside  I don t think there s a possibility that was thought of    You could try hacking with the AllocConsole P Invoke which will open a console even when your current application is a GUI application  The Console class will then post to the now opened console

User · Answer

NOTE  The original answer below should work for any version of Visual  Studio up through Visual  Studio  2012  Visual  Studio  2013 does not appear to have a Test Results window any more  Instead  if you need test-specific output you can use  Stretch s suggestion of Trace Write   to write output to the Output window   The Console Write method does not write to the  quot console quot  -- it writes to whatever is hooked up to the standard output handle for the running process  Similarly  Console Read reads input from whatever is hooked up to the standard input  When you run a unit test through Visual  Studio  2010  standard output is redirected by the test harness and stored as part of the test output  You can see this by right-clicking the Test Results window and adding the column named  quot Output  StdOut  quot  to the display  This will show anything that was written to standard output  You could manually open a console window  using P Invoke as sinni800 says  From reading the AllocConsole documentation  it appears that the function will reset stdin and stdout handles to point to the new console window   I m not 100  sure about that  it seems kind of wrong to me if I ve already redirected stdout for Windows to steal it from me  but I haven t tried   In general  though  I think it s a bad idea  if all you want to use the console for is to dump more information about your unit test  the output is there for you  Keep using Console WriteLine the way you are  and check the output results in the Test Results window when it s done

User · Answer

Debug WriteLine   can be used as well

User · Answer

I have an easier solution  that I used myself recently  for a host of lazy reasons    Add this method to the class you are working in  public static void DumbDebug string message        File WriteAllText   quot C  AdHocConsole  quot    message    quot  txt quot    quot this is really dumb  I wish Microsoft had more obvious solutions to its solutions problems  quot       Then   open up the directory AdHocConsole  and order by created time  Make sure when you add your  print statements   They are distinct though  else there will be juggling

User · Answer

Someone commented about this apparently new functionality in Visual  Studio  2013  I wasn t sure what he meant at first  but now that I do  I think it deserves its own answer  We can use Console WriteLine normally and the output is displayed  just not in the Output window  but in a new window after we click  quot Output quot  in the test details

User · Answer

As stated  unit tests are designed to run without interaction  However  you can debug unit tests  just like any other code  The easiest way is to use the Debug button in the Test Results tab  Being able to debug means being able to use breakpoints   Being able to use breakpoints  then  means being able to use Tracepoints  which I find extremely useful in every day debugging  Essentially  Tracepoints allow you to write to the Output window  or  more accurately  to standard output   Optionally  you can continue to run  or you can stop like a regular breakpoint  This gives you the  quot functionality quot  you are asking for  without the need to rebuild your code  or fill it up with debug information  Simply add a breakpoint  and then right-click on that breakpoint  Select the  quot When Hit    quot  option   Which brings up the dialog   A few things to note   Notice that the breakpoint is now shown as a diamond  instead of a sphere  indicating a trace point You can output the value of a variable by enclosing it like  this   Uncheck the  quot Continue Execution quot  checkbox to have the code break on this line  like any regular breakpoint You have the option of running a macro  Please be careful - you may cause harmful side effects   See the documentation for more details

User · Answer

You can use Trace WriteLine    to write to the Output window when debugging a unit test

[c#] Can I write into the console in a unit test? If yes, why doesn't the console window open?

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