add test_cli_runner for testing app.cli commands

CHANGES.rst

@@ -137,6 +137,8 @@ unreleased
   development server over HTTPS. (`#2606`_)
 - Added :data:`SESSION_COOKIE_SAMESITE` to control the ``SameSite``
   attribute on the session cookie. (`#2607`_)
+- Added :meth:`~flask.Flask.test_cli_runner` to create a Click runner
+  that can invoke Flask CLI commands for testing. (`#2636`_)
 
 .. _pallets/meta#24: https://github.com/pallets/meta/issues/24
 .. _#1421: https://github.com/pallets/flask/issues/1421
@@ -178,6 +180,7 @@ unreleased
 .. _#2581: https://github.com/pallets/flask/pull/2581
 .. _#2606: https://github.com/pallets/flask/pull/2606
 .. _#2607: https://github.com/pallets/flask/pull/2607
+.. _#2636: https://github.com/pallets/flask/pull/2636
 
 
 Version 0.12.2

docs/api.rst

@@ -188,6 +188,15 @@ Test Client
    :members:
 
 
+Test CLI Runner
+---------------
+
+.. currentmodule:: flask.testing
+
+.. autoclass:: FlaskCliRunner
+    :members:
+
+
 Application Globals
 -------------------
 

docs/testing.rst

@@ -413,15 +413,17 @@ with ``get_json``.
 Testing CLI Commands
 --------------------
 
-Click comes with `utilities for testing`_ your CLI commands.
+Click comes with `utilities for testing`_ your CLI commands. A
+:class:`~click.testing.CliRunner` runs commands in isolation and
+captures the output in a :class:`~click.testing.Result` object.
 
-Use :meth:`CliRunner.invoke <click.testing.CliRunner.invoke>` to call
-commands in the same way they would be called from the command line. The
-:class:`~click.testing.CliRunner` runs the command in isolation and
-captures the output in a :class:`~click.testing.Result` object. ::
+Flask provides :meth:`~flask.Flask.test_cli_runner` to create a
+:class:`~flask.testing.FlaskCliRunner` that passes the Flask app to the
+CLI automatically. Use its :meth:`~flask.testing.FlaskCliRunner.invoke`
+method to call commands in the same way they would be called from the
+command line. ::
 
     import click
-    from click.testing import CliRunner
 
     @app.cli.command('hello')
     @click.option('--name', default='World')
@@ -429,14 +431,22 @@ captures the output in a :class:`~click.testing.Result` object. ::
         click.echo(f'Hello, {name}!')
 
     def test_hello():
-        runner = CliRunner()
+        runner = app.test_cli_runner()
+
+        # invoke the command directly
         result = runner.invoke(hello_command, ['--name', 'Flask'])
         assert 'Hello, Flask' in result.output
 
+        # or by name
+        result = runner.invoke(args=['hello'])
+        assert 'World' in result.output
+
+In the example above, invoking the command by name is useful because it
+verifies that the command was correctly registered with the app.
+
 If you want to test how your command parses parameters, without running
-the command, use the command's :meth:`~click.BaseCommand.make_context`
-method. This is useful for testing complex validation rules and custom
-types. ::
+the command, use its :meth:`~click.BaseCommand.make_context` method.
+This is useful for testing complex validation rules and custom types. ::
 
     def upper(ctx, param, value):
         if value is not None:

flask/app.py

@@ -311,6 +311,14 @@ class Flask(_PackageBoundObject):
     #: .. versionadded:: 0.7
     test_client_class = None
 
+    #: The :class:`~click.testing.CliRunner` subclass, by default
+    #: :class:`~flask.testing.FlaskCliRunner` that is used by
+    #: :meth:`test_cli_runner`. Its ``__init__`` method should take a
+    #: Flask app object as the first argument.
+    #:
+    #: .. versionadded:: 1.0
+    test_cli_runner_class = None
+
     #: the session interface to use.  By default an instance of
     #: :class:`~flask.sessions.SecureCookieSessionInterface` is used here.
     #:
@@ -983,6 +991,23 @@ class Flask(_PackageBoundObject):
             from flask.testing import FlaskClient as cls
         return cls(self, self.response_class, use_cookies=use_cookies, **kwargs)
 
+    def test_cli_runner(self, **kwargs):
+        """Create a CLI runner for testing CLI commands.
+        See :ref:`testing-cli`.
+
+        Returns an instance of :attr:`test_cli_runner_class`, by default
+        :class:`~flask.testing.FlaskCliRunner`. The Flask app object is
+        passed as the first argument.
+
+        .. versionadded:: 1.0
+        """
+        cls = self.test_cli_runner_class
+
+        if cls is None:
+            from flask.testing import FlaskCliRunner as cls
+
+        return cls(self, **kwargs)
+
     def open_session(self, request):
         """Creates or opens a new session.  Default implementation stores all
         session data in a signed cookie.  This requires that the

flask/testing.py

@@ -12,6 +12,9 @@
 
 import werkzeug
 from contextlib import contextmanager
+
+from click.testing import CliRunner
+from flask.cli import ScriptInfo
 from werkzeug.test import Client, EnvironBuilder
 from flask import _request_ctx_stack
 from flask.json import dumps as json_dumps
@@ -193,3 +196,36 @@ class FlaskClient(Client):
         top = _request_ctx_stack.top
         if top is not None and top.preserved:
             top.pop()
+
+
+class FlaskCliRunner(CliRunner):
+    """A :class:`~click.testing.CliRunner` for testing a Flask app's
+    CLI commands. Typically created using
+    :meth:`~flask.Flask.test_cli_runner`. See :ref:`testing-cli`.
+    """
+    def __init__(self, app, **kwargs):
+        self.app = app
+        super(FlaskCliRunner, self).__init__(**kwargs)
+
+    def invoke(self, cli=None, args=None, **kwargs):
+        """Invokes a CLI command in an isolated environment. See
+        :meth:`CliRunner.invoke <click.testing.CliRunner.invoke>` for
+        full method documentation. See :ref:`testing-cli` for examples.
+
+        If the ``obj`` argument is not given, passes an instance of
+        :class:`~flask.cli.ScriptInfo` that knows how to load the Flask
+        app being tested.
+
+        :param cli: Command object to invoke. Default is the app's
+            :attr:`~flask.app.Flask.cli` group.
+        :param args: List of strings to invoke the command with.
+
+        :return: a :class:`~click.testing.Result` object.
+        """
+        if cli is None:
+            cli = self.app.cli
+
+        if 'obj' not in kwargs:
+            kwargs['obj'] = ScriptInfo(create_app=lambda: self.app)
+
+        return super(FlaskCliRunner, self).invoke(cli, args, **kwargs)

tests/test_testing.py

@@ -8,15 +8,16 @@
     :copyright: © 2010 by the Pallets team.
     :license: BSD, see LICENSE for more details.
 """
-
+import click
 import pytest
 
 import flask
 import werkzeug
 
 from flask._compat import text_type
+from flask.cli import ScriptInfo
 from flask.json import jsonify
-from flask.testing import make_test_environ_builder
+from flask.testing import make_test_environ_builder, FlaskCliRunner
 
 
 def test_environ_defaults_from_config(app, client):
@@ -335,3 +336,47 @@ def test_nosubdomain(app, client):
 
     assert 200 == response.status_code
     assert b'xxx' == response.data
+
+
+def test_cli_runner_class(app):
+    runner = app.test_cli_runner()
+    assert isinstance(runner, FlaskCliRunner)
+
+    class SubRunner(FlaskCliRunner):
+        pass
+
+    app.test_cli_runner_class = SubRunner
+    runner = app.test_cli_runner()
+    assert isinstance(runner, SubRunner)
+
+
+def test_cli_invoke(app):
+    @app.cli.command('hello')
+    def hello_command():
+        click.echo('Hello, World!')
+
+    runner = app.test_cli_runner()
+    # invoke with command name
+    result = runner.invoke(args=['hello'])
+    assert 'Hello' in result.output
+    # invoke with command object
+    result = runner.invoke(hello_command)
+    assert 'Hello' in result.output
+
+
+def test_cli_custom_obj(app):
+    class NS(object):
+        called = False
+
+    def create_app():
+        NS.called = True
+        return app
+
+    @app.cli.command('hello')
+    def hello_command():
+        click.echo('Hello, World!')
+
+    script_info = ScriptInfo(create_app=create_app)
+    runner = app.test_cli_runner()
+    runner.invoke(hello_command, obj=script_info)
+    assert NS.called