Testing Click Applications¶
For basic testing, Click provides the
click.testing module which
provides test functionality that helps you invoke command line
applications and check their behavior.
These tools should really only be used for testing as they change the entire interpreter state for simplicity and are not in any way thread-safe!
The basic functionality for testing Click applications is the
CliRunner which can invoke commands as command line scripts. The
CliRunner.invoke() method runs the command line script in isolation
and captures the output as both bytes and binary data.
The return value is a
Result object, which has the captured output
data, exit code, and optional exception attached.
import click from click.testing import CliRunner def test_hello_world(): @click.command() @click.argument('name') def hello(name): click.echo('Hello %s!' % name) runner = CliRunner() result = runner.invoke(hello, ['Peter']) assert result.exit_code == 0 assert result.output == 'Hello Peter!\n'
For subcommand testing, a subcommand name must be specified in the args parameter of
import click from click.testing import CliRunner def test_sync(): @click.group() @click.option('--debug/--no-debug', default=False) def cli(debug): click.echo('Debug mode is %s' % ('on' if debug else 'off')) @cli.command() def sync(): click.echo('Syncing') runner = CliRunner() result = runner.invoke(cli, ['--debug', 'sync']) assert result.exit_code == 0 assert 'Debug mode is on' in result.output assert 'Syncing' in result.output
File System Isolation¶
For basic command line tools that want to operate with the file system, the
CliRunner.isolated_filesystem() method comes in useful which sets up
an empty folder and changes the current working directory to.
import click from click.testing import CliRunner def test_cat(): @click.command() @click.argument('f', type=click.File()) def cat(f): click.echo(f.read()) runner = CliRunner() with runner.isolated_filesystem(): with open('hello.txt', 'w') as f: f.write('Hello World!') result = runner.invoke(cat, ['hello.txt']) assert result.exit_code == 0 assert result.output == 'Hello World!\n'
The test wrapper can also be used to provide input data for the input stream (stdin). This is very useful for testing prompts, for instance:
import click from click.testing import CliRunner def test_prompts(): @click.command() @click.option('--foo', prompt=True) def test(foo): click.echo('foo=%s' % foo) runner = CliRunner() result = runner.invoke(test, input='wau wau\n') assert not result.exception assert result.output == 'Foo: wau wau\nfoo=wau wau\n'
Note that prompts will be emulated so that they write the input data to the output stream as well. If hidden input is expected then this obviously does not happen.