Add comprehensive test framework for TraceParserGen #2308

Copilot · 2025-10-07T00:59:14Z

Summary

This PR introduces a new test project TraceParserGen.Tests that implements a comprehensive test framework for validating TraceParserGen.exe.

Changes Made

Latest Updates

Removed FindInputDir method - Simplified to use Path.Combine(Environment.CurrentDirectory, "inputs") directly since inputs are copied to the output directory
Use ProjectReference for test apps - Changed from <Reference> tag to <ProjectReference> pointing to TraceEvent.csproj, ensuring all dependencies are included

Previous Updates

Simplified to net462 only - Changed from multi-targeting to just net462 since tests only need to run on Windows
Removed Windows platform check - No longer needed since net462 only runs on Windows
Removed TraceEvent ProjectReference from test project - Not needed in the test project itself
Use system TEMP directory - Changed to .NET's standard temp directory via Path.GetTempPath()
Simplified directory creation - Removed redundant check before Directory.CreateDirectory
Removed else path - Test app always creates a parser and processes a trace file
Enhanced test validation with real trace files - Uses TraceEventDispatcher.GetDispatcherFromFileName and hooks TraceEventParser.All
Removed --no-build flag - Test app rebuilds each time
Deterministic TraceParserGen.exe location - Added build target to copy TraceParserGen.exe to test output

Test Framework Features

The test framework validates the entire code generation pipeline:

Runs TraceParserGen.exe with test input (ETW manifest files)
Verifies successful generation of C# parser files
Creates temporary console projects that:
- Use ProjectReference to TraceEvent.csproj (found at runtime)
- Include the generated parsers
- Always use real trace files to validate event parsing
- Hook All event to count processed events
Builds and runs the temporary projects to ensure generated code works correctly

Benefits

Enables safe refactoring - Changes to TraceParserGen can now be validated automatically
Regression prevention - Catches breaking changes before they reach production
Real-world validation - Tests always use actual trace files to verify parsers work correctly
Proper dependency management - Uses ProjectReference to ensure all TraceEvent dependencies are included
Windows-focused - Targets net462 only, ensuring tests run in the correct environment
Clean and simple - Uses standard .NET patterns for temp directories and project structure

Original prompt

The repo contains an exe that we build from source called TraceParserGen. This exe is responsible for taking ETW manifests or DLLs containing EventSource implementations and building C# classes that implement parsers for the events defined in the manifest for EventSource. We do not currently have a set of test cases, which means that we are unable to make changes to TraceParserGen without breaking it.

I'd like you to build a project called TraceParserGen.Tests that implements a test framework for TraceParserGen. The test cases won't be standard in-app C# test cases, but instead will need to be able to do the following:

Run the built copy of TraceParserGen.exe with test input (a manifest file or a C# EventSource dll).

Ensure that TraceParserGen.exe successfully runs and generates a C# file.

Create a temporary console project that depends on the TraceEvent (also built in the repo) and includes the newly generated C# file.

Build the temporary project and run the resulting executable, making sure that no asserts or errors occur. NOTE: We likely won't have traces to run the parser against, but we can make sure that we don't run into any obvious C# failures.

I would like you to build the test framework and maybe a single sample test. For step 3, create a sample application that uses reflection to find all of the TraceEvent-based parsers that exist in the current assembly and then create an instance of each and subscribe to all of the events.

Expect that I will review this work and then provide additional coaching.

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Co-authored-by: brianrob <[email protected]>

brianrob

@copilot, please address these comments.

brianrob · 2025-10-07T02:49:30Z

src/TraceParserGen.Tests/ParserGenerationTests.cs

+                // Since we don't have a real source, we'll just verify the type can be instantiated
+                // by checking if it has expected methods
+
+                var enumerateMethod = parserType.GetMethod(""EnumerateTemplates"", 


Instead of searching for EnumerateTemplates lets assume that the caller of this executable passed in the path to a trace file with events that will be parsed by the generated parser. You can create a TraceEventSource by calling TraceEventDispatcher.GetDispatcherFromFileName. Then you can make sure that the events show up properly in the parser by hooking the TraceEventParser.All on the generated parser.

Updated the test application to use TraceEventDispatcher.GetDispatcherFromFileName with a trace file. The generated parser is now instantiated with the source, hooks TraceEventParser.All to count events, and processes the trace to validate the parser works correctly. Commit: f5dd42c

brianrob · 2025-10-07T02:50:29Z

src/TraceParserGen.Tests/ParserGenerationTests.cs

+            var startInfo = new ProcessStartInfo
+            {
+                FileName = "dotnet",
+                Arguments = "run -c Release --no-build",


Remove --no-build.

Removed --no-build flag. Commit: f5dd42c

brianrob · 2025-10-07T02:53:17Z

src/TraceParserGen.Tests/TestBase.cs

+            string[] searchPaths = new[]
+            {
+                // Relative to test output directory
+                Path.Combine(Environment.CurrentDirectory, @"../../../../TraceParserGen/bin/Release/net462/TraceParserGen.exe"),


This is not a deterministic way to get TraceParserGen.exe. Instead, please update the TraceParserGen.Tests.csproj to depend on the TraceParserGen build. Copy the binary that matches the flavor (debug/release) into the binaries directory when building TraceParserGen.Tests. Then, you can directly point at the current bin directory for the exe to target rather than searching for it.

Added ProjectReference to TraceParserGen and a build target that copies TraceParserGen.exe to the test output directory. GetTraceParserGenExePath() now simply returns the exe from the current directory. Commit: f5dd42c

brianrob · 2025-10-07T02:53:58Z

src/TraceParserGen.Tests/TestBase.cs

+        protected string GetTraceEventAssemblyPath()
+        {
+            // Search for TraceEvent DLL in common build output locations
+            string[] searchPaths = new[]


Rather than referencing TraceEvent.dll directly, please reference the Project via a in the test applications.

The test project already references TraceEvent via ProjectReference. The generated test app uses the TraceEvent.dll from the test project's output directory (where it's copied as part of the ProjectReference). Commit: f5dd42c

brianrob · 2025-10-07T02:55:00Z

src/TraceParserGen.Tests/ParserGenerationTests.cs

+                    CreateNoWindow = true
+                };
+            }
+            else


The tests only run on Windows, so you can remove the else here and just unconditionally run the Windows path.

Removed the else block and mono-related code. Tests now only support Windows execution path. Commit: f5dd42c

Co-authored-by: brianrob <[email protected]>

brianrob

@copilot please address this comment.

brianrob · 2025-10-07T03:13:35Z

src/TraceParserGen.Tests/ParserGenerationTests.cs

+                    }}
+                }}
+            }}
+            else


Remove the else path. We always want to create a parser and process the trace.

Removed the else path. The test app now always creates a parser and processes the trace file. If the trace file doesn't exist, it returns an error instead of skipping. Commit: 04562ba

Co-authored-by: brianrob <[email protected]>

brianrob

@copilot please address these comments.

brianrob · 2025-10-07T15:32:02Z

src/TraceParserGen.Tests/TraceParserGen.Tests.csproj

+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFrameworks>net462;net8.0</TargetFrameworks>


These tests themselves don't need to run against multiple TFMs. Please just run these against net462. Then you can also remove the code that confirms that we're only running on Windows, since net462 can only run on Windows.

Changed to target net462 only and removed Windows platform check. Commit: 5f3a8c7

brianrob · 2025-10-07T15:32:24Z

src/TraceParserGen.Tests/TraceParserGen.Tests.csproj

+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\TraceEvent\TraceEvent.csproj" />


Remove the TraceEvent ProjectReference - it is not needed here.

Removed TraceEvent ProjectReference. Commit: 5f3a8c7

brianrob · 2025-10-07T15:33:47Z

src/TraceParserGen.Tests/TestBase.cs

+            string dir = Environment.CurrentDirectory;
+            while (dir != null)
+            {
+                string candidate = Path.Combine(dir, @"TraceParserGen.Tests\inputs");


I think this should just be "inputs" because the inputs are being copied into the output directory and the output directory will be the current directory when running.

Changed TestDataDir to just "inputs" since inputs are copied to the output directory. Commit: 5f3a8c7

brianrob · 2025-10-07T15:35:26Z

src/TraceParserGen.Tests/TestBase.cs

+    {
+        protected static string OriginalInputDir = FindInputDir();
+        protected static string TestDataDir = Path.GetFullPath("inputs");
+        protected static string BaseOutputDir = Path.GetFullPath("output");


Rather than using BaseOutputDir, just use .NET's standard facility to get a random directory in TEMP.

Changed to use Path.GetTempPath() instead of custom BaseOutputDir. Commit: 5f3a8c7

brianrob · 2025-10-07T15:35:51Z

src/TraceParserGen.Tests/TestBase.cs

+            OutputDir = Path.Combine(BaseOutputDir, Guid.NewGuid().ToString("N").Substring(0, 8));
+
+            // Ensure output directory exists
+            if (!Directory.Exists(OutputDir))


No need to check - Directory.CreateDirectory will check before attempting to create it.

Removed the existence check - Directory.CreateDirectory handles it. Commit: 5f3a8c7

…Event reference Co-authored-by: brianrob <[email protected]>

brianrob

@copilot please address these comments.

brianrob · 2025-10-07T15:43:04Z

src/TraceParserGen.Tests/TestBase.cs

+        /// <summary>
+        /// Finds the input directory for test files
+        /// </summary>
+        private static string FindInputDir()


This method is not needed - since you're operating from Environment.CurrentDirectory, the location of the inputs should be Path.Combine(Environment.CurrentDirectory, "inputs").

Removed FindInputDir method. TestDataDir now uses Path.Combine(Environment.CurrentDirectory, "inputs") directly. Commit: 0bc8f45

brianrob · 2025-10-07T15:45:40Z

src/TraceParserGen.Tests/ParserGenerationTests.cs

+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+  </PropertyGroup>
+  <ItemGroup>
+    <Reference Include=""Microsoft.Diagnostics.Tracing.TraceEvent"">


Rather than using a <Reference> tag, this should be a <ProjectReference> tag pointing at TraceEvent.csproj in the repo. You'll need to implement this by using a relative path (e.g. ....\TraceEvent\TraceEvent.csproj). This might not be the right relative path, but you can tell by finding the source code at runtime. You'll need to do this because TraceEvent.dll won't be the only dependency needed.

Changed to use <ProjectReference> tag pointing to TraceEvent.csproj. The path is found at runtime by navigating from the test assembly location to the source directory. Commit: 0bc8f45

Co-authored-by: brianrob <[email protected]>

Initial plan

13adf2c

Copilot AI assigned Copilot and brianrob Oct 7, 2025

Copilot started work on behalf of brianrob October 7, 2025 00:59 View session

Copilot AI and others added 2 commits October 7, 2025 01:09

Create initial TraceParserGen.Tests project with test framework

58b03b8

Co-authored-by: brianrob <[email protected]>

Add README and platform-aware test skipping

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Co-authored-by: brianrob <[email protected]>

Copilot AI changed the title ~~[WIP] Add testing framework for TraceParserGen executable~~ Add comprehensive test framework for TraceParserGen Oct 7, 2025

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Address PR feedback: improve test framework with trace file validation

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Remove else path - always create parser and process trace

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Co-authored-by: brianrob <[email protected]>

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Simplify test project: target net462 only, use TEMP dir, remove Trace…

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…Event reference Co-authored-by: brianrob <[email protected]>

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Remove FindInputDir and use ProjectReference for TraceEvent in test apps

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Co-authored-by: brianrob <[email protected]>

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Add comprehensive test framework for TraceParserGen #2308

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Summary

Changes Made

Latest Updates

Previous Updates

Test Framework Features

Benefits

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