Crate assert_cmd

Assert Command - Easy command initialization and assertions.

assert_cmd aims to simplify the process for doing integration testing of CLIs, including:

• Finding your crate’s binary to test
• Assert on the result of your program’s run.

Overview

Create a Command:

• Command::new(path)
• Command::from_std(...)
• Command::cargo_bin(name)

Configure a Command:

• arg / args
• current_dir
• env / envs / env_remove / env_clear
• write_stdin / pipe_stdin
• timeout

Validate a Command:

• ok / unwrap / unwrap_err
• assert
  • success, see Assert
  • failure, see Assert
  • interrupted, see Assert
  • code, see Assert
  • stdout, see Assert
  • stderr, see Assert
  • get_output for everything else, see Assert

Note: Command is provided as a convenience. Extension traits for std::process::Command and Output are provided for interoperability:

• CommandCargoExt
• OutputOkExt
• OutputAssertExt

Examples

Here’s a trivial example:

use assert_cmd::Command;

let mut cmd = Command::cargo_bin("bin_fixture").unwrap();
cmd.assert().success();

And a little of everything:

use assert_cmd::Command;

let mut cmd = Command::cargo_bin("bin_fixture").unwrap();
let assert = cmd
    .arg("-A")
    .env("stdout", "hello")
    .env("exit", "42")
    .write_stdin("42")
    .assert();
assert
    .failure()
    .code(42)
    .stdout("hello\n");

Relevant crates

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

• escargot for more control over configuring the crate’s binary.
• duct for orchestrating multiple processes.
  • or commandspec for easier writing of commands
• rexpect for testing interactive programs.
• assert_fs for filesystem fixtures and assertions.
  • or tempfile for scratchpad directories.
• dir-diff for testing file side-effects.

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:

• 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.

Re-exports

• pub use crate::cmd::Command;

Modules

• assert
  std::process::Output assertions.
• cargo
  Simplify running bins in a Cargo project.
• cmd
  std::process::Command customized for testing.
• output
  Simplify one-off runs of programs.
• prelude
  Extension traits that are useful to have available.

Macros

• crate_name
  Allows you to pull the name from your Cargo.toml at compile time.