emx-testspec

A testspec engine for CLI E2E testing, inspired by Go's cmd/internal/script and roguepeppe/go-internal/testscript.

Overview

emx-testspec provides a declarative scripting DSL for testing CLI tools. Tests are written as txtar archives where the comment section contains script commands and the file section provides test fixtures.

Features

• ✅ Declarative syntax - Simple, readable test scripts
• ✅ Txtar integration - Test fixtures in the same file
• ✅ Rich command set - exec, stdout, stderr, cmp, grep, etc.
• ✅ Platform conditions - Conditional execution per OS/arch
• ✅ Virtual files - stdout and stderr as file-like objects
• ✅ Background processes - Run commands asynchronously
• ✅ Flexible matching - Regex patterns with multi-line support
• ✅ MIT License - Free to use in any project

Installation

Add to your Cargo.toml:

[dependencies]
emx-testspec = "0.1"

Or use via Git:

[dependencies]
emx-testspec = { git = "https://github.com/coreseekdev/emx-testspec" }

Requires emx-txtar as a dependency.

Quick Start

Basic Test

Create tests/mytool.txtar:

# Test basic functionality
exec mytool input.txt
stdout 'success'
-- input.txt --
test data

Run tests:

use emx_testspec::run_and_assert;#[test]fntest_mytool(){run_and_assert("tests");}

Using as CLI

Install the CLI:

cargo install emx-testspec --git https://github.com/coreseekdev/emx-testspec

Run tests:

emx-testspec tests/ # Run all tests
emx-testspec tests/test.txtar # Run single test
emx-testspec tests/ -v # Verbose output
emx-testspec tests/ -f "basic"# Filter by name
emx-testspec tests/ --keep # Preserve work directories

Script Syntax

Commands

Command	Description	Example
exec	Execute a command	exec mytool arg1 arg2
stdout	Match stdout with regex	stdout 'expected'
stderr	Match stderr with regex	stderr 'error message'
cmp	Compare files	cmp file1 file2
cmpenv	Compare with env expansion	cmpenv file1 file2
grep	Search in file	grep 'pattern' file
cat	Print file contents	cat file
cd	Change directory	cd subdir
cp	Copy files	cp src dst
mv	Move/rename files	mv old new
rm	Remove files	rm file
mkdir	Create directories	mkdir dir
exists	Check file existence	exists file
env	Set/get environment	env KEY=value
echo	Print to stdout buffer	echo text
sleep	Wait for duration	sleep 1s
stop	Stop test (non-error)	stop 'reason'
skip	Skip test	skip 'reason'
help	List commands	help

Prefixes

• ! - Command must fail (exit code ≠ 0)
• ? - Command may succeed or fail
• No prefix - Command must succeed (exit code = 0)

Example:

exec mytool --valid # Must succeed
! exec mytool --invalid # Must fail
? exec mytool --unpredictable # Either is OK

Conditions

Conditional execution based on platform:

[unix] exec unix-tool
[windows] exec windows-tool
[linux] exec linux-tool
[amd64] exec x86_64-tool
[!windows] exec not-windows-tool
[exec:python] exec python-script

Environment Variables

Built-in Variables

• $WORK or $TMPDIR - Temporary working directory
• $PWD - Current working directory
• ${/} - OS path separator (/ or \)
• ${:} - Path list separator (: or ;)

Usage

env KEY=value
echo $KEY

In comparison:

cmp stdout $WORK/expected.txt

Virtual Files

stdout and stderr can be used as virtual files:

exec mytool
cmp stdout expected.txt
cp stderr debug.log

Advanced Usage

Background Processes

exec server &
sleep 2s
exec client --request
wait

Multi-line Matching

exec mytool
stdout 'line1.*line2.*line3'

File Comparison with Diff

exec mytool input.txt
cmp stdout output.txt

If files differ, unified diff is shown.

Environment Expansion

env NAME=World
echo "Hello $NAME"

In cmpenv, environment variables are expanded before comparison.

API Usage

Running Tests

use emx_testspec::{TestRunner,RunConfig};let config = RunConfig{dir:"tests".into(),filter:None,workdir_root:None,preserve_work:false,verbose:false,extensions:vec![".txtar".into()],setup:None,};let runner = TestRunner::new(config);let result = runner.run_all()?;assert!(result.all_passed());

Custom Commands

use emx_testspec::{Engine,Cmd,CmdResult};use anyhow::Result;structMyCustomCmd;implCmdforMyCustomCmd{fnusage(&self) -> (String,String){("mycmd".into(),"[args]".into())}fnrun(&self,args:&[String],state:&mutState) -> Result<CmdResult>{// Custom logic hereOk(CmdResult::Success)}}// Register custom commandletmut engine = Engine::new();
engine.register_command("mycmd",Box::new(MyCustomCmd));

Environment Variables for Testing

Variable	Effect
TESTSCRIPT_VERBOSE=1	Enable verbose logging
TESTSCRIPT_WORK=1	Preserve working directories

Format Specification

See spec/00-princ-11-tool-testspec.mx for the full grammar specification.

BNF Grammar

script-line = prefix? condition* command-name arg* inline-comment?
prefix = "!" | "?"
condition = "[" "!"? cond-name (":" suffix)? "]"
command = identifier
arg = quoted-arg | unquoted-arg
quoted-arg = "'" (char | "''")* "'"

Documentation

• API Documentation
• Grammar Specification

License

MIT License - see LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Related Projects

• emx-txtar - Txtar archive format
• Go testscript - Original inspiration
• roguepeppe/go-internal/testscript - Enhanced Go version