Crate assert_cmd

Assert Command - Easy command initialization and assertions.

assert_cmd includes support for:

• Setting up your program-under-test (see CommandCargoExt, CommandStdInExt).
• Verifying your program-under-test (see OutputOkExt, OutputAssertExt).

[dependencies]
assert_cmd = "0.10"

Overview

Create a Command:

• Command::new(path), see Command
• Command::main_binary(), see CommandCargoExt
• Command::cargo_bin(name), see CommandCargoExt
• Command::cargo_example(name), see CommandCargoExt

Configure a Command:

• arg / args, see Command
• current_dir, see Command
• env / envs / env_remove / env_clear, see Command
• with_stdin, see CommandStdInExt

Validate either a Command or Output:

• ok / unwrap / unwrap_err, see OutputOkExt
• assert (OutputAssertExt)
  • success, see Assert
  • failure, see Assert
  • interrupted, see Assert
  • code, see Assert
  • stdout, see Assert
  • stderr, see Assert

Examples

Here’s a trivial example:

extern crate assert_cmd;

use std::process::Command;
use assert_cmd::prelude::*;

fn main() {
    let mut cmd = Command::main_binary().unwrap();
    cmd.assert().success();
}

And a little of everything:

extern crate assert_cmd;

use std::process::Command;
use assert_cmd::prelude::*;

fn main() {
    let mut cmd = Command::main_binary().unwrap();
    cmd
        .arg("-A")
        .env("stdout", "hello")
        .env("exit", "42")
        .with_stdin()
        .buffer("42");
    let assert = cmd.assert();
    assert
        .failure()
        .code(42)
        .stdout("hello\n");
}

Relevant crates

Other crates that might be useful in testing command line programs.

• duct for orchestrating multiple processes.
• commandspec for easier writing of commands
• assert_fs for filesystem fixtures and assertions.
• dir-diff for testing file side-effects.
• tempfile for scratchpad directories.

Migrating from assert_cli v0.6

assert_cmd is the successor to the original assert_cli:

• More flexible, reusable assertions (also used by assert_fs).
• Can integrate with other process-management crates, like duct.
• Addresses several architectural problems.

Key points in migrating from assert_cli:

• Command is extended with traits rather than being wrapping in custom logic.
• The command-under-test is run eagerly, with assertions happening immediately.
• success() is not implicit and requires being explicitly called.
• stdout/stderr aren’t automatically trimmed before being passed to the Predicate.