testscript-rs

A Rust crate for testing command-line tools using filesystem-based script files.

testscript-rs provides a framework for writing integration tests for CLI applications using a simple DSL using the .txtar format, where test scripts and file contents are combined in a single file.

This crate is inspired by and aims to be compatible with Go's github.com/rogpeppe/go-internal/testscript package, which was itself extracted from internal packages in the Go stdlib, having originally been written by Russ Cox.

Testscript is primarily useful for describing testing scenarios involving executing commands and dealing with files. This makes it a good choice for testing CLI applications in a succinct and human-readable way.

Quick Example

Given a file testdata/simple.txt:

echo "hello"    # print "hello"
stdout "hello"  # check that stdout includes "hello"

You can run this in your tests:

use testscript_rs::testscript;

#[test]
fn test_my_cli() {
    testscript::run("testdata")
        .execute()
        .unwrap();
}

The test will find every testscript file in ./testdata, and execute it.

A more realistic example might look like this:

use testscript_rs::testscript;

#[test]
fn test_my_cli() {
    testscript::run("testdata")
        .setup(|env| {
            // Set environment variables for tests
            env.set_env_var("MY_APP_CONFIG", "/path/to/config");
            
            // Compile your CLI tool
            std::process::Command::new("cargo")
                .args(["build", "--bin", "my-cli"])
                .status()?;

            // Copy binary to test environment
            std::fs::copy("target/debug/my-cli", env.work_dir.join("my-cli"))?;
            Ok(())
        })
        .execute()
        .unwrap();
}

With a test script in testdata/basic.txt:

# Test basic functionality
exec ./my-cli --version
stdout "my-cli 1.0"

exec ./my-cli process input.txt
cmp output.txt expected.txt

-- input.txt --
test content

-- expected.txt --
processed: test content

Running the test will compile the CLI program, make it available to the testscript environment, run the specified commands, and check its output.

Installation

Add testscript-rs to your Cargo.toml:

[dev-dependencies]
testscript-rs = "<release>"

Requires Rust 1.70 or later.

Usage

With Custom Commands

testscript::run("testdata")
    .command("custom-cmd", |env, args| {
        // Your custom command implementation, e.g., the entrypoint of your CLI, so you don't have to `cargo build` it as above.
        println!("Running custom command with args: {:?}", args);
        Ok(())
    })
    .condition("feature-enabled", true)
    .preserve_work_on_failure(true)  // Debug failed tests
    .execute()
    .unwrap();

To call the custom command, in your testscript file:

custom-cmd arg1 arg2 arg3

Test Script Format

Test scripts use the txtar format. For complete format documentation, see the original Go testscript documentation.

Built-in Commands

• exec - Execute external commands
• cmp - Compare two files
• stdout/stderr - Check command output (supports regex and -count=N option)
• exists - Check file existence
• mkdir - Create directories
• cp - Copy files (supports stdout/stderr as source)
• mv - Move/rename files
• rm - Remove files/directories
• chmod - Change file permissions
• env - Set environment variables (supports ${VAR@R} regex quoting)
• cmpenv - Compare files with environment variable substitution
• stdin - Set stdin for next command
• cd - Change working directory
• wait - Wait for background processes
• kill - Kill background processes
• skip - Skip test execution
• stop - Stop test early (pass)
• unquote - Remove leading > from file lines
• grep - Search files with regex
• symlink - Create symbolic links

Commands can be prefixed with conditions ([unix]) or negated (!).

Go testscript Compatibility

testscript-rs implements full compatibility with Go's testscript package, including:

• ${VAR@R} syntax - Escape regex metacharacters in environment variables
• -count=N option - Count exact number of matches for stdout/stderr
• Regex pattern detection - Automatic detection based on regex metacharacters
• Environment variable substitution - Full $VAR and ${VAR} support
• Whitespace handling - Matches Go's exact trimming behavior

Error Messages

testscript-rs provides detailed, readable error messages with script context to make debugging easy:

Error in testdata/hello.txt at line 6:
  3 | stdout "this works"
  4 |
  5 | # This command will fail
> 6 | exec nonexistent-command arg1 arg2
  7 | stdout "should not get here"
  8 |

Command 'nonexistent-command' failed: command not found

Output Comparison Errors

When stdout/stderr assertions fail, you get clear, formatted output comparisons:

Error in testdata/test.txt at line 3:
  1 | exec echo "hello world"
  2 |
> 3 | stdout "goodbye world"

Expected: 'goodbye world'
  Actual: 'hello world'

For multi-line output, line numbers are shown:

Expected:
  1 | line1
  2 | expected
  3 | line3

Actual:
  1 | line1
  2 | actual
  3 | line3

Optional Color Support

Enable colored error output for terminal-friendly debugging:

[dev-dependencies]
testscript-rs = { version = "<release>", features = ["colors"] }

With colors enabled, the failing line and error details are highlighted in red for easy identification.

Note: Some features of testscript in Go are not supported in this Rust port:

• [gc] for whether Go was built with gc
• [gccgo] for whether Go was built with gccgo
• [go1.x] for whether the Go version is 1.x or later

Examples

See examples/sample-cli/ and its testdata directory for more examples.

There are also more tests in testdata that demonstrate and check this implementations behavior.

UpdateScripts for Easier Test Maintenance

UpdateScripts automatically updates test files with actual command output, making test maintenance easier:

// Enable via API
testscript::run("testdata")
    .update_scripts(true)
    .execute()
    .unwrap();

Or via environment variable:

UPDATE_SCRIPTS=1 cargo test

When enabled, instead of failing on output mismatches, the test files will be updated with actual command output:

Before (failing test):

exec my-tool --version
stdout "my-tool 1.0"

After running with update mode:

exec my-tool --version
stdout "my-tool 2.1.0"

This feature only updates stdout and stderr expectations while preserving file structure and comments.