How can I write output from a unit test

Question

Any call in my unit tests to either Debug Write line  or Console Write Line  simply gets skipped over while debugging and the output is never printed  Calls to these functions from within classes I m using work fine  I understand that unit testing is meant to be automated  but I still would like to be able to output messages from a unit test

User · Answer

In Visual Studio 2017  you can see the output from test explorer   1  In your test method  Console WriteLine  something      2  Run the test   3  In Test Explorer window  click the Passed Test Method   4  And click the  Output  link     And click  Output   you can see the result of Console Writeline

User · Answer

I get no output when my Test Test Settings Default Processor Architecture setting and the assemblies that my test project references are not the same  Otherwise Trace Writeline   works fine

User · Answer

Console WriteLine won t work  Only Debug WriteLine   or Trace WriteLine   will work  in debug mode   I do the following  include using System Diagnostics in the test module  Then  use Debug WriteLine for my output  right click on the test  choose Debug Selected Tests  The result output will now appear in the Output window below  I use Visual Studio 2017 vs 15 8 1  with the default unit test framework VS provides

User · Answer

In VS 2019  in the main VS menu bar click  View - gt  Test Explorer Right-click your test method in Test Explorer - gt  Debug Click the additional output link as seen in the screenshot below    You can use   Debug WriteLine Console WriteLine TestContext WriteLine  all will log to the additional output window

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If you re running tests with dotnet test  you may find that Console Error WriteLine produces output  This is how I ve worked around the issue with NUnit tests  which also seem to have all Debug  Trace and stdout output suppressed

User · Answer

Try using  Console WriteLine   The call to Debug WriteLine will only be made during when DEBUG is defined  Other suggestions are to use  Trace WriteLine as well  but I haven t tried this  There is also an option  not sure if Visual  Studio  2008 has it   but you can still Use Debug WriteLine when you run the test with Test With Debuggeroption in the IDE

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I ve accidentally found that DebugView  with enabled Capture  gt  Capture Win32 option  will capture writes to System Console  Example test   Test  public void FooTest         for  int i   0  i  lt  5  i            Console WriteLine   quot   DateTime UtcNow ToString  quot G quot     Hello World quot

User · Answer

Try using TestContext WriteLine   which outputs text in test results  Example   TestClass  public class UnitTest1       private TestContext testContextInstance            lt summary gt          Gets or sets the test context which provides         information about and functionality for the current test run           lt  summary gt      public TestContext TestContext               get   return testContextInstance            set   testContextInstance   value                TestMethod      public void TestMethod1                 TestContext WriteLine  quot Message    quot             The  quot magic quot  is described in MSDN   To use TestContext  create a member and property within your test class       The test framework automatically sets the property  which you can then use in unit tests

User · Answer

A different variant of the cause solution  My issue was that I was not getting an output because I was writing the result set from an asynchronous LINQ call to the console in a loop in an asynchronous context  var p    context Payment Where pp   gt  pp applicationNumber Trim       quot 12345 quot     p ForEachAsync payment   gt  Console WriteLine payment Amount     And so the test was not writing to the console before the console object was cleaned up by the runtime  when running only one test   The solution was to convert the result set to a list first  so I could use the non-asynchronous version of forEach    var p    context Payment Where pp   gt  pp applicationNumber Trim       quot 12345 quot   ToList     p ForEachAsync payment   gt Console WriteLine payment Amount

User · Answer

It is indeed depending on the test runner as  jonzim mentioned  For NUnit 3 I had to use NUnit Framework TestContext Progress WriteLine   to get running output in the Output window of Visual Studio 2017  NUnit describes how to  here To my understanding this revolves around the added parallelization of test execution the test runners have received

User · Answer

Are you sure you re running your unit tests in Debug  Debug WriteLine won t be called in Release builds  Two options to try are   Trace WriteLine    which is built into release builds as well as debug  Undefine DEBUG in your build settings for the unit test

User · Answer

It depends on your test runner    for instance  I m using xUnit  so in case that s what you are using  follow these instructions  https   xunit github io docs capturing-output html This method groups your output with each specific unit test  using Xunit  using Xunit Abstractions   public class MyTestClass       private readonly ITestOutputHelper output       public MyTestClass ITestOutputHelper output                this output   output              Fact      public void MyTest                 var temp    quot my class  quot           output WriteLine  quot This is output from  0  quot   temp            There s another method listed in the link I provided for writing to your Output window  but I prefer the previous

User · Answer

I was also trying to get Debug or Trace or Console or TestContext to work in unit testing  None of these methods would appear to work or show output in the output window      Trace WriteLine  quot test trace quot        Debug WriteLine  quot test debug quot        TestContext WriteLine  quot test context quot        Console WriteLine  quot test console quot     Visual Studio 2012 and greater  from comments  In Visual Studio 2012  there is no icon  Instead  there is a link in the test results called Output  If you click on the link  you see all of the WriteLine  Prior to Visual Studio 2012 I then noticed in my Test Results window  after running the test  next to the little success green circle  there is another icon  I doubled clicked it  It was my test results  and it included all of the types of writelines above

User · Answer

Trace WriteLine should work provided you select the correct output  the dropdown labeled with  quot Show output from quot  found in the Output window

User · Answer

I m using xUnit so this is what I use  Debugger Log 0   quot 1 quot   input    PS  you can use Debugger Break    too  so you can see your log in out

User · Answer

Solved with the following example  public void CheckConsoleOutput         Console WriteLine  quot Hello  World  quot        Trace WriteLine  quot Trace Trace the World quot        Debug WriteLine  quot Debug Debug World quot        Assert IsTrue true      After running this test  under  Test Passed   there is the option to view the output  which will bring up the output window

User · Answer

I think it is still actual  You can use this NuGet package  Bitoxygen Testing Pane Call the custom WriteLine method from this library  It creates a Testing pane inside the Output window and puts messages there always  during each test  it runs independently of DEBUG and TRACE flags   To make tracing more easy I can recommend to create a base class   TestClass  public abstract class BaseTest        region Properties     public TestContext TestContext   get  set         public string Class               get   return this TestContext FullyQualifiedTestClassName              public string Method               get   return this TestContext TestName               endregion       region Methods     protected virtual void Trace string message                System Diagnostics Trace WriteLine message            Output Testing Trace WriteLine message              endregion     TestClass  public class SomeTest   BaseTest        TestMethod      public void SomeTest1                 this Trace string Format  quot Yeah   0  and  1  quot   this Class  this Method

[c#] How can I write output from a unit test?

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