FsHotWatch.TestPrune 0.2.0-alpha.1

FsHotWatch.TestPrune

Plugin for test impact analysis. When you change a source file, TestPrune figures out which tests are affected and runs only those -- instead of your entire test suite.

Why

Running all tests after every save is slow. If you change a single function, you probably only need to run 3 tests out of 500. TestPrune uses the warm FSharpChecker's symbol analysis to track which tests depend on which symbols, so it can tell you exactly what to re-run.

How it works

1. You save a file
2. TestPrune receives FileChecked with the warm compiler's results
3. It analyzes which symbols changed
4. It looks up which test classes reference those symbols
5. If testConfigs are provided, it runs only the affected tests
6. It emits TestCompleted for downstream plugins (like Coverage)

Configuration

In .fs-hot-watch.json:

{
  "tests": {
    "beforeRun": "dotnet build",
    "projects": [
      {
        "project": "MyApp.Tests",
        "command": "dotnet",
        "args": "run --project tests/MyApp.Tests --no-build --",
        "filterTemplate": "--filter-class {classes}",
        "classJoin": " ",
        "group": "unit"
      }
    ]
  }
}

CLI

# Run all affected tests
fs-hot-watch test

# Run tests for a specific project group
fs-hot-watch test -p MyApp.Tests

# Run only previously-failed tests
fs-hot-watch test --only-failed

# Query which tests are affected by recent changes
fs-hot-watch affected-tests

Programmatic usage

From the FullPipelineExample:

daemon.RegisterHandler(
    TestPrunePlugin.create
        ".fshw/test-impact.db"   // database path
        repoRoot                  // repo root
        (Some [                   // test configs
            { Project = "MyApp.Tests"
              Command = "dotnet"
              Args = "run --project tests/MyApp.Tests --no-build --"
              Group = "unit"
              Environment = []
              FilterTemplate = Some "--filter-class {classes}"
              ClassJoin = " " }
        ])
        None                      // symbol snapshot
        None                      // beforeRun callback
        None                      // coverage args
        None                      // coverage args generator
        None                      // getCommitId for caching
)

Install

dotnet add package FsHotWatch.TestPrune