Why is this forked?

This is hard forked from github.com/rogpeppe/testscript to allow the gh maintainers to explore the use of testscript in gh, while providing the flexibility for us to share modifications and extensions. It is not intended to be a long-term maintained fork and you should not rely on it.

If we determine it is a good fit for the project, we will decide what to do next based on how our needs align with the preferences of the maintainers of rogpeppe/testscript.

Original README with minor tweaks to indicate upstream/fork relationship

This repository factors out an opinionated selection of internal packages and functionality from the Go standard
library. Currently this consists mostly of packages and testing code from within the Go tool implementation.

The upstream repo is primarily maintained by long-time
Go contributors who are also currently
maintaining CUE (which is primarily written in Go
and which relies upon several of the packages here).

Contributions are welcome, but please open an issue for discussion first.

Packages

Included are the following:

• goproxytest: a GOPROXY implementation designed for test use.
• gotooltest: Use the Go tool inside test scripts (see testscript below)
• imports: list of known architectures and OSs, and support for reading import statements.
• par: do work in parallel.
• testenv: information on the current testing environment.
• testscript: script-based testing based on txtar files
• txtar: simple text-based file archives for testing.

Note that most users of txtar should use https://pkg.go.dev/golang.org/x/tools/txtar instead.
Our package will be replaced by it once https://github.com/golang/go/issues/59264 is fixed.

testscript

The most popular package here is the testscript package:

• Provides a shell-like test environment that is very nicely tuned for testing Go CLI commands.
• Extracted from the core Go team’s internal testscript package (cmd/go/internal/script),
  which is heavily used to test the go command.
• Supports patterns for checking stderr/stdout, command pass/fail assertions, and so on.
• Integrates well with go test, including coverage support.
• Inputs and sample output files can use the simple txtar
  text archive format, also used by the Go playground.
• Allows automatically updating
  golden files.
• Built-in support for Go concepts like build tags.
• Accompanied by a testscript command
  for running standalone scripts with files embedded in txtar format.

A nice introduction to using testscripts is this blog post series.
Both testscript and txtar were originally created
by Russ Cox.