Diff tool not launching

[CrispyDrone]

I can't seem to get the diff tool to launch when running Verify. I'm using version 31.28.0 of TUnit.Verify on Windows 11. As far as I understand, VisualStudio should work automatically without DiffEngineTray.

I've also tried manually calling DiffRunner.Launch on the verified and received files but nothing happens either.

When I check the resolved tools, it lists neovim and VisualStudio in that order.

Am I supposed to add some more configuration or launch the tool explicitly (I expect not)?

I've read most of the documentation and looked through issues. I found this one talking about verifying a byte array #1562 which is also what I'm doing (the byte array represents a UTF-8 encoded file without a BOM). It also mentioned diff tools not launching.

edit: When I install DiffEngineTray, it does allow me to accept or discard the received file, but there's also no option to see a diff. Perhaps it's not supposed to work for binary arrays?

edit2: When I instead verify it as text, it indeed launches neovim, so it does seem to work properly on my machine; the only question that remains is about whether there's any support for visualizing binary files.

[SimonCropp]

Verify(byte[]) defaults the extension to bin, and no text diff tool registers .bin, so DiffEngine has nothing to launch — that's why the tray offers accept/discard but no diff. Pass an extension instead: await Verify(bytes, extension: "txt").

[SimonCropp]

the only question that remains is about whether there's any support for visualizing binary files.

the idea of diff tool launching is to show something that is understandable to a person. it is rare that raw binary meets that requirement

[CrispyDrone]

Sorry about editing my original post twice. I think you're right that it's rarely useful. I've been working with unicode the past few weeks and so have been using a hex editor here and there so didn't think twice about it.

Thanks again for the quick replies!

[SimonCropp]

If a hex view is genuinely what's wanted, a custom tool can be registered for a hex extension. Two pieces are needed: the tool itself, and an empty .hex template — for the "new snapshot" case DiffEngine calls AllFiles.TryCreateFile to materialize the missing verified side, and bails with NoEmptyFileForExtension if it can't.

Note the leading dot: binaryExtensions is matched against Path.GetExtension, so ".hex", not "hex".

Option A — clone an already-resolving tool. Beyond Compare has a hex compare mode and is already a known tool, so this is the least work:

using System.Runtime.CompilerServices;
using DiffEngine;
using EmptyFiles;

public static class ModuleInit
{
    [ModuleInitializer]
    public static void Init()
    {
        var emptyHex = Path.Combine(Path.GetTempPath(), "empty.hex");
        File.WriteAllBytes(emptyHex, []);
        AllFiles.UseFile(Category.Binary, emptyHex);

        DiffTools.AddToolBasedOn(
            DiffTool.BeyondCompare,
            name: "BeyondCompareHex",
            binaryExtensions: [".hex"]);
    }
}

Option B — a standalone tool by path:

[ModuleInitializer]
public static void Init()
{
    var emptyHex = Path.Combine(Path.GetTempPath(), "empty.hex");
    File.WriteAllBytes(emptyHex, []);
    AllFiles.UseFile(Category.Binary, emptyHex);

    DiffTools.AddTool(
        name: "HexDiff",
        autoRefresh: false,
        isMdi: false,
        supportsText: false,
        requiresTarget: true,
        useShellExecute: true,
        launchArguments: new(
            Left: (temp, target) => $"\"{target}\" \"{temp}\"",
            Right: (temp, target) => $"\"{temp}\" \"{target}\""),
        exePath: @"%ProgramFiles%\VBinDiff\vbindiff.exe",
        binaryExtensions: [".hex"]);
}

Then:

await Verify(bytes, extension: "hex");

AddTool/AddToolBasedOn return null when exePath doesn't resolve, and that null is exactly the silent no-diff failure mode from the original issue, so it's worth asserting on. exePath supports %EnvVar% expansion and * wildcards.

Docs:

• Custom diff tool: https://github.com/VerifyTests/DiffEngine/blob/main/docs/diff-tool.custom.md
• Resolution order (tools are prepended, so the last added wins): https://github.com/VerifyTests/DiffEngine/blob/main/docs/diff-tool.custom.md#resolution-order
• AllFiles.UseFile: https://github.com/VerifyTests/EmptyFiles#usefile

One aside: Beyond Compare's built-in definition already registers .bin, so plain Verify(bytes) would have launched a diff for anyone with BC installed. neovim and Visual Studio simply don't claim any binary extensions.

[CrispyDrone]

Thanks for the detailed explanation! I will play around with both options.