Expose basic api for testing external plugins.phil/plugin-testing-api

We want external plugins to be able to make use of the core testing utils.
This commit exposes the basic utilities which are currently in use in
bst-external plugins. If necessary, more utilities could be exposed in the
future.

Moves the following files from tests/testutils/ to
buildstream/plugintestingutils/:
o runcli.py
o integration.py

As part of this, this commit makes the following changes to runcli.py
and integration.py:
o runcli.py: Fix linting errors
o runcli.py: Add user facing documentation
o Integration.py: Add user facing documentation

1 files changed, 30 insertions, 0 deletions

diff --git a/buildstream/plugintestutils/__init__.py b/buildstream/plugintestutils/__init__.py
new file mode 100644
index 000000000..c7238a29c
--- /dev/null
+++ b/buildstream/plugintestutils/__init__.py
@@ -0,0 +1,30 @@
+#
+#  Copyright (C) 2019 Codethink Limited
+#  Copyright (C) 2019 Bloomberg Finance LP
+#
+#  This program is free software; you can redistribute it and/or
+#  modify it under the terms of the GNU Lesser General Public
+#  License as published by the Free Software Foundation; either
+#  version 2 of the License, or (at your option) any later version.
+#
+#  This library is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+#  Lesser General Public License for more details.
+#
+#  You should have received a copy of the GNU Lesser General Public
+#  License along with this library. If not, see <http://www.gnu.org/licenses/>.
+
+
+from .runcli import cli, cli_integration
+
+# To make use of these test utilities it is necessary to have pytest
+# available. However, we don't want to have a hard dependency on
+# pytest.
+try:
+    import pytest
+except ImportError:
+    module_name = globals()['__name__']
+    msg = "Could not import pytest:\n" \
+          "To use the {} module, you must have pytest installed.".format(module_name)
+    raise ImportError(msg)