CODEWITHSUNDEEP
windowsdebuggingtestingrustvisual-studio-code
Riduidel
Riduidel

Reputation: 22292

How to debug Rust unit tests on Windows?

I'm developing code for the Codingame problems using VS Code on Windows with Rust and the Visual Studio toolchain.

I have found multiple guides explaining how to debug the executable generated by cargo build, the best being Debug Rust on Windows with Visual Studio Code and the MSVC Debugger.

However, when I face problems, I tend to write unit tests (I've done that in Java, JavaScript, Ruby, ...), which I then debug. Unfortunately, I can't find any way to do that in Rust. How do I configure my environment to debug my tests?

I'm not talking about adding println! statements in my tests, as I already know how to do that. I'm also not talking about adding new assertions, because those reside in the test, not in the tested code.

What I want is to use the VS Code Debugger on the code called by my test.

Upvotes: 22

Views: 13729

Answers (3)

opedroso
opedroso

Reputation: 103

When using WinDBG, consider using rust-windbg. It's script will do all the heavy lifting of setting up the WinDBG environment such that you can concentrate on debugging your source's issue.

Upvotes: 0

Cesc
Cesc

Reputation: 1190

Expanding on Shepmaster's answer you could automate the process of finding the right executable.

In nushell you could do something like this.

export def open-in-windbg [executable: path] {
   # NOTE: change it to your executable location if it differs
   ~/AppData/Local/Microsoft/WindowsApps/WinDbgX.exe $executable
}

export def --wrapped "cargo test-windbg" [...args: string] {
  let executable = (cargo t ...$args --no-run e>| parse --regex 'Executable.*\((?<name>.+)\)' | get 0.name)
  open-in-windbg $executable
}

And then call

cargo test-windb

Extra cargo test flags should be fine too

cargo test-windbg --features myfeat

NOTE: I did not manage to make Windbg open the source file yet.

Upvotes: 0

Shepmaster
Shepmaster

Reputation: 430671

Rust unit tests are compiled as separate binaries, which means you debug them exactly the same as any other binary. Once compiled, they are located at ./target/debug/$name-$hash.

Visual Studio Code

Here's modified versions of the VS Code configuration files that allow me to debug a unit test.

tasks.json

{
    "type": "shell",
    "label": "cargo test build",
    "command": "cargo",
    "args": [
        "test", "--no-run"
    ],
    "problemMatcher": [
        "$rustc"
    ]
}

launch.json

{
    "name": "Run Test Debugger",
    "type": "cppvsdbg",
    "request": "launch",
    "program": "${workspaceFolder}/target/debug/buggin-70708b3916187eeb.exe",
    "args": [],
    "stopAtEntry": false,
    "cwd": "${workspaceFolder}",
    "environment": [],
    "externalConsole": true,
    "preLaunchTask": "cargo test build",
}

Working

VS Code debugger running on a test

Windbg

Build your tests:

cargo test --no-run

Open the built executable in Windbg and open the source file.

Windbg on Rust test

Finding the hash is the most annoying aspect. The best solution I know of is to write a small script that builds the tests and then finds the test executable based on which is newest. My Powershell skills are not adequate to the task, nor do I know how to directly integrate this with VS Code or Windbg.

There are open issues for Cargo to help with identifying the file:

Upvotes: 23

Related Questions