Bug 1696251 - Add tests to mach command decorators. r=mhentges

In preparation for future changes in how these decorators work,
add a few basic tests.

Differential Revision: https://phabricator.services.mozilla.com/D107377

python/mach/mach/test/python.ini

@@ -5,6 +5,7 @@ subsuite = mach
 [test_conditions.py]
 skip-if = python == 3
 [test_config.py]
+[test_decorators.py]
 [test_dispatcher.py]
 [test_entry_point.py]
 [test_error_output.py]

python/mach/mach/test/test_decorators.py

@@ -0,0 +1,119 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from __future__ import absolute_import, unicode_literals
+
+import os
+
+import pytest
+from mock import Mock
+
+from mozbuild.base import MachCommandBase
+from mozunit import main
+
+import mach.registrar
+import mach.decorators
+from mach.base import MachError
+from mach.decorators import CommandArgument, CommandProvider, Command, SubCommand
+
+
+@pytest.fixture
+def registrar(monkeypatch):
+    test_registrar = mach.registrar.MachRegistrar()
+    test_registrar.register_category(
+        "testing", "Mach unittest", "Testing for mach decorators"
+    )
+    monkeypatch.setattr(mach.decorators, "Registrar", test_registrar)
+    return test_registrar
+
+
+def test_register_command_with_argument(registrar):
+    inner_function = Mock()
+    context = Mock()
+    context.cwd = "."
+
+    @CommandProvider
+    class CommandFoo(MachCommandBase):
+        @Command("cmd_foo", category="testing")
+        @CommandArgument("--arg", default=None, help="Argument help.")
+        def run_foo(self, arg):
+            inner_function(arg)
+
+    registrar.dispatch("cmd_foo", context, arg="argument")
+
+    inner_function.assert_called_with("argument")
+
+
+def test_register_command_with_metrics_path(registrar):
+    context = Mock()
+    context.cwd = "."
+
+    metrics_path = "metrics/path"
+    metrics_mock = Mock()
+    context.telemetry.metrics.return_value = metrics_mock
+
+    @CommandProvider(metrics_path=metrics_path)
+    class CommandFoo(MachCommandBase):
+        @Command("cmd_foo", category="testing")
+        def run_foo(self):
+            assert self.metrics == metrics_mock
+
+    registrar.dispatch("cmd_foo", context)
+
+    context.telemetry.metrics.assert_called_with(metrics_path)
+    assert context.handler.metrics_path == metrics_path
+
+
+def test_register_command_sets_up_class_at_runtime(registrar):
+    inner_function = Mock()
+
+    context = Mock()
+    context.cwd = "."
+
+    # Inside the following class, we test that the virtualenv is set up properly
+    # dynamically on the instance that actually runs the command.
+    @CommandProvider
+    class CommandFoo(MachCommandBase):
+        @Command("cmd_foo", category="testing", virtualenv_name="env_foo")
+        def run_foo(self):
+            assert (
+                os.path.basename(self.virtualenv_manager.virtualenv_root) == "env_foo"
+            )
+            inner_function("foo")
+
+        @Command("cmd_bar", category="testing", virtualenv_name="env_bar")
+        def run_bar(self):
+            assert (
+                os.path.basename(self.virtualenv_manager.virtualenv_root) == "env_bar"
+            )
+            inner_function("bar")
+
+    registrar.dispatch("cmd_foo", context)
+    inner_function.assert_called_with("foo")
+    registrar.dispatch("cmd_bar", context)
+    inner_function.assert_called_with("bar")
+
+
+def test_cannot_create_command_nonexisting_category(registrar):
+    with pytest.raises(MachError):
+
+        @CommandProvider
+        class CommandFoo(MachCommandBase):
+            @Command("cmd_foo", category="bar")
+            def run_foo(self):
+                pass
+
+
+def test_subcommand_requires_parent_to_exist(registrar):
+    with pytest.raises(MachError):
+
+        @CommandProvider
+        class CommandFoo(MachCommandBase):
+            @SubCommand("sub_foo", "foo")
+            def run_foo(self):
+                pass
+
+
+if __name__ == "__main__":
+    main()