mtp-hot-reload

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Translated

Suggests using Microsoft Testing Platform (MTP) hot reload to iterate fixes on failing tests without rebuilding. Use when user says "hot reload tests", "iterate on test fix", "run tests without rebuilding", "speed up test loop", "fix test faster", or needs to set up MTP hot reload to rapidly iterate on test failures. Covers setup (NuGet package, environment variable, launchSettings.json) and the iterative workflow for fixing tests. DO NOT USE FOR: writing test code, diagnosing test failures, CI/CD pipeline configuration, or Visual Studio Test Explorer hot reload (which is a different feature).

2installs

Sourcedotnet/skills

Added on2026-03-20

NPX Install

npx skill4agent add dotnet/skills mtp-hot-reload

SKILL.md Content

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MTP Hot Reload for Iterative Test Fixing

Set up and use Microsoft Testing Platform hot reload to rapidly iterate fixes on failing tests without rebuilding between each change.

When to Use

User has one or more failing tests and wants to iterate fixes quickly
User wants to avoid rebuild overhead while fixing test code or production code
User asks about hot reload for tests or speeding up the test-fix loop
User needs to set up MTP hot reload in their project

When Not to Use

User needs to write new tests from scratch (use general coding assistance)
User needs to diagnose why a test is failing (use diagnostic skills)
User wants Visual Studio Test Explorer hot reload (different feature, built into VS)
Project uses VSTest — hot reload requires Microsoft Testing Platform (MTP)
User needs CI/CD pipeline configuration

Inputs

Input	Required	Description
Test project path	No	Path to the test project (.csproj). Defaults to current directory.
Failing test name or filter	No	Specific test(s) to iterate on

Workflow

Step 1: Verify the project uses Microsoft Testing Platform

Hot reload requires MTP. It does not work with VSTest.

Check the same detection signals as the

run-tests

skill:

SDK 10+:

global.json

→

"test": { "runner": "Microsoft.Testing.Platform" }

SDK 8/9:

<TestingPlatformDotnetTestSupport>true</TestingPlatformDotnetTestSupport>

in

.csproj

,

Directory.Build.props

, or

Directory.Packages.props

Other signals:

<Sdk Name="MSTest.Sdk">

,

<EnableMSTestRunner>true</EnableMSTestRunner>

, TUnit package reference

If the project uses VSTest, inform the user that MTP hot reload is not available and suggest migrating to MTP first, or using Visual Studio's built-in Test Explorer hot reload feature instead.

Step 2: Add the hot reload NuGet package

Install the

Microsoft.Testing.Extensions.HotReload

package:

shell

dotnet add <project-path> package Microsoft.Testing.Extensions.HotReload

Note: When using
Microsoft.Testing.Platform.MSBuild
(included transitively by MSTest, NUnit, and xUnit runners), the extension is auto-registered when you install its NuGet package — no code changes needed.

Step 3: Enable hot reload

Hot reload is activated by setting the

TESTINGPLATFORM_HOTRELOAD_ENABLED

environment variable to

.

Option A — Set it in the shell before running tests:

shell

# PowerShell
$env:TESTINGPLATFORM_HOTRELOAD_ENABLED = "1"

# bash/zsh
export TESTINGPLATFORM_HOTRELOAD_ENABLED=1

Option B — Add it to
launchSettings.json
(recommended for repeatable use):

Create or update

Properties/launchSettings.json

in the test project:

json

{
  "profiles": {
    "<ProjectName>": {
      "commandName": "Project",
      "environmentVariables": {
        "TESTINGPLATFORM_HOTRELOAD_ENABLED": "1"
      }
    }
  }
}

Step 4: Run the tests with hot reload

Run the test project directly (not through

dotnet test

) to use hot reload in console mode:

shell

dotnet run --project <project-path>

To filter to specific failing tests, pass the filter after

--

:

Framework	Filter syntax
MSTest	`dotnet run --project <path> -- --filter "FullyQualifiedName~TestMethodName"`
NUnit	`dotnet run --project <path> -- --filter "FullyQualifiedName~TestMethodName"`
xUnit v3	`dotnet run --project <path> -- --filter-method "*TestMethodName"`
TUnit	`dotnet run --project <path> -- --treenode-filter "///ClassName/TestMethodName"`

The test host will start, run the tests, and remain running waiting for code changes.

Step 5: Iterate on the fix

Edit the source code (test code or production code) in your editor
The test host detects the changes and re-runs the affected tests automatically
Review the updated results in the console
Repeat until all targeted tests pass

Important: Hot reload currently works in console mode only. There is no support for hot reload in Test Explorer for Visual Studio or Visual Studio Code.

Step 6: Finalize

Once all tests pass:

Stop the test host (Ctrl+C)
Run a full
```
dotnet test
```
to confirm all tests pass with a clean build
Optionally remove
```
TESTINGPLATFORM_HOTRELOAD_ENABLED
```
from the environment or keep
```
launchSettings.json
```
for future use

Validation

Project uses Microsoft Testing Platform (not VSTest)
```
Microsoft.Testing.Extensions.HotReload
```
package is installed
```
TESTINGPLATFORM_HOTRELOAD_ENABLED
```
environment variable is set to
```
1
```
Tests run and the host remains active waiting for changes
Code changes are picked up without manual restart

Common Pitfalls

Pitfall	Solution
Using `dotnet test` instead of `dotnet run`	Hot reload requires `dotnet run --project <path>` to run the test host directly in console mode
Project uses VSTest, not MTP	Hot reload requires MTP. Migrate to MTP first or use VS Test Explorer hot reload
Forgetting to set the environment variable	Set `TESTINGPLATFORM_HOTRELOAD_ENABLED=1` before running
Expecting Test Explorer integration	Console mode only — no VS/VS Code Test Explorer support
Making unsupported code changes (rude edits)	Some changes (adding new types, changing method signatures) require a restart. Stop and re-run

mtp-hot-reload

NPX Install

Tags

SKILL.md Content

MTP Hot Reload for Iterative Test Fixing

When to Use

When Not to Use

Inputs

Workflow

Step 1: Verify the project uses Microsoft Testing Platform

Step 2: Add the hot reload NuGet package

Step 3: Enable hot reload

Step 4: Run the tests with hot reload

Step 5: Iterate on the fix

Step 6: Finalize

Validation

Common Pitfalls