Add standard output and error when a test fails and does not display it (#7847)

## Summary of changes

We get [some CI errors
](https://dev.azure.com/datadoghq/dd-trace-dotnet/_build/results?buildId=191248&view=logs&j=5635f724-ec42-5e82-7816-fb263b6cfcc0&t=e80b9b00-921f-539a-741c-f91926c040ef)in
tests caused by a non 0 exit code from a sample but we get no output
from the sample itself.

This PR improves error reporting when tests fail due to non-zero exit
codes by ensuring that process stdout and stderr are logged to the test
output before assertions fail. This makes debugging CI failures
significantly easier, especially for signal-related crashes (SIGABRT,
SIGSEGV, etc.).

## Reason for change

## Implementation details

## Test coverage

## Other details
<!-- Fixes #{issue} -->


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Author: NachoEchevarria

profiler/test/Datadog.Profiler.IntegrationTests/Helpers/TestApplicationRunner.cs

@@ -235,9 +235,16 @@ private void RunTest(MockDatadogAgent agent)
                 throw new XunitException("An error occured during the test. See the error output above.");
             }
 
-            Assert.True(
-                0 == process.ExitCode,
-                $"Exit code of \"{Path.GetFileName(process.StartInfo?.FileName ?? string.Empty)}\" should be 0 instead of {process.ExitCode} (= 0x{process.ExitCode.ToString("X")})");
+            if (process.ExitCode != 0)
+            {
+                _output.WriteLine($"[TestRunner] Process exited with code {process.ExitCode} (0x{process.ExitCode:X})");
+                _output.WriteLine($"[TestRunner] Standard output:\n{standardOutput}");
+                _output.WriteLine($"[TestRunner] Error output:\n{errorOutput}");
+
+                Assert.True(
+                    false,
+                    $"Exit code of \"{Path.GetFileName(process.StartInfo?.FileName ?? string.Empty)}\" should be 0 instead of {process.ExitCode} (= 0x{process.ExitCode:X})");
+            }
         }
 
         private void SetEnvironmentVariables(StringDictionary environmentVariables, MockDatadogAgent agent)

tracer/test/Datadog.Trace.Debugger.IntegrationTests/Helpers/DebuggerSampleProcessHelper.cs

@@ -8,6 +8,7 @@
 using System.Net;
 using System.Threading.Tasks;
 using Datadog.Trace.TestHelpers;
+using Xunit.Abstractions;
 
 namespace Datadog.Trace.Debugger.IntegrationTests.Helpers
 {
@@ -17,12 +18,14 @@ internal class DebuggerSampleProcessHelper : ProcessHelper
 
         private readonly string _stopUrl;
         private readonly string _runUrl;
+        private readonly ITestOutputHelper _output;
 
-        public DebuggerSampleProcessHelper(string baseUrl, Process process, Action<string> onDataReceived = null)
+        public DebuggerSampleProcessHelper(string baseUrl, Process process, ITestOutputHelper output, Action<string> onDataReceived = null)
             : base(process, onDataReceived)
         {
             _stopUrl = $"{baseUrl}{StopSuffix}";
             _runUrl = baseUrl;
+            _output = output;
         }
 
         internal async Task StopSample()
@@ -36,6 +39,13 @@ internal async Task StopSample()
                 throw new InvalidOperationException($"The process did not exit after {timeout}ms");
             }
 
+            if (Process.ExitCode != 0)
+            {
+                _output.WriteLine($"[DebuggerSampleProcessHelper] Process exited with code {Process.ExitCode} (0x{Process.ExitCode:X})");
+                _output.WriteLine($"[DebuggerSampleProcessHelper] Standard output:\n{StandardOutput}");
+                _output.WriteLine($"[DebuggerSampleProcessHelper] Error output:\n{ErrorOutput}");
+            }
+
             ExitCodeException.ThrowIfNonZero(Process.ExitCode);
         }
 

tracer/test/Datadog.Trace.Debugger.IntegrationTests/Helpers/DebuggerTestHelper.cs

@@ -68,7 +68,7 @@ internal static async Task<DebuggerSampleProcessHelper> StartSample(TestHelper h
         var listenUrl = $"{localHost}:{listenPort}/";
 
         var process = await helper.StartSample(agent, $"--test-name {testName} --listen-url {listenUrl}", string.Empty, aspNetCorePort: 5000);
-        var processHelper = new DebuggerSampleProcessHelper(listenUrl, process);
+        var processHelper = new DebuggerSampleProcessHelper(listenUrl, process, helper.GetOutput());
 
         return processHelper;
     }

tracer/test/Datadog.Trace.TestHelpers.AutoInstrumentation/TestHelper.cs

@@ -71,6 +71,8 @@ protected TestHelper(EnvironmentHelper environmentHelper, ITestOutputHelper outp
 
         protected ITestOutputHelper Output { get; }
 
+        public ITestOutputHelper GetOutput() => Output;
+
         public virtual void Dispose()
         {
         }