tests: extract testutils.override_os_uname

Combine the very similar override_uname_arch() and override_uname_os()
in a new helper function, to reduce duplication.

Also use a 'try/finally' block to ensure that the original
os.uname() is restored.

This will make it simpler to adopt platform.uname() instead in later
work.

4 files changed, 66 insertions, 45 deletions

diff --git a/tests/format/optionarch.py b/tests/format/optionarch.py
index 86363b834..3f779e5ea 100644
--- a/tests/format/optionarch.py
+++ b/tests/format/optionarch.py
@@ -1,7 +1,6 @@
 # Pylint doesn't play well with fixtures and dependency injection from pytest
 # pylint: disable=redefined-outer-name
 
-from contextlib import contextmanager
 import os
 
 import pytest
@@ -10,29 +9,14 @@ from buildstream import _yaml
 from buildstream._exceptions import ErrorDomain, LoadErrorReason
 from buildstream.plugintestutils.runcli import cli  # pylint: disable=unused-import
 
+from tests.testutils import override_os_uname
+
 # Project directory
 DATA_DIR = os.path.dirname(os.path.realpath(__file__))
 
 
-# Context manager to override the reported value of `os.uname()`
-@contextmanager
-def override_uname_arch(name):
-    orig_uname = os.uname
-    orig_tuple = tuple(os.uname())
-    override_result = (orig_tuple[0], orig_tuple[1],
-                       orig_tuple[2], orig_tuple[3],
-                       name)
-
-    def override():
-        return override_result
-
-    os.uname = override
-    yield
-    os.uname = orig_uname
-
-
 @pytest.mark.datafiles(DATA_DIR)
-@pytest.mark.parametrize("uname,value,expected", [
+@pytest.mark.parametrize("machine,value,expected", [
     # Test explicitly provided arches
     ('arm', 'aarch32', 'Army'),
     ('arm', 'aarch64', 'Aarchy'),
@@ -46,8 +30,8 @@ def override_uname_arch(name):
     ('i386', 'aarch32', 'Army'),
     ('x86_64', 'aarch64', 'Aarchy'),
 ])
-def test_conditional(cli, datafiles, uname, value, expected):
-    with override_uname_arch(uname):
+def test_conditional(cli, datafiles, machine, value, expected):
+    with override_os_uname(machine=machine):
         project = os.path.join(datafiles.dirname, datafiles.basename, 'option-arch')
 
         bst_args = []
@@ -70,7 +54,7 @@ def test_conditional(cli, datafiles, uname, value, expected):
 @pytest.mark.datafiles(DATA_DIR)
 def test_unsupported_arch(cli, datafiles):
 
-    with override_uname_arch("x86_64"):
+    with override_os_uname(machine="x86_64"):
         project = os.path.join(datafiles.dirname, datafiles.basename, 'option-arch')
         result = cli.run(project=project, silent=True, args=[
             'show',
@@ -85,7 +69,7 @@ def test_unsupported_arch(cli, datafiles):
 @pytest.mark.datafiles(DATA_DIR)
 def test_alias(cli, datafiles):
 
-    with override_uname_arch("arm"):
+    with override_os_uname(machine="arm"):
         project = os.path.join(datafiles.dirname, datafiles.basename, 'option-arch-alias')
         result = cli.run(project=project, silent=True, args=[
             'show',
@@ -100,7 +84,7 @@ def test_alias(cli, datafiles):
 @pytest.mark.datafiles(DATA_DIR)
 def test_unknown_host_arch(cli, datafiles):
 
-    with override_uname_arch("x86_128"):
+    with override_os_uname(machine="x86_128"):
         project = os.path.join(datafiles.dirname, datafiles.basename, 'option-arch')
         result = cli.run(project=project, silent=True, args=[
             'show',
diff --git a/tests/format/optionos.py b/tests/format/optionos.py
index 989989a99..a4e2a6cf9 100644
--- a/tests/format/optionos.py
+++ b/tests/format/optionos.py
@@ -1,7 +1,6 @@
 # Pylint doesn't play well with fixtures and dependency injection from pytest
 # pylint: disable=redefined-outer-name
 
-from contextlib import contextmanager
 import os
 
 import pytest
@@ -10,27 +9,13 @@ from buildstream import _yaml
 from buildstream._exceptions import ErrorDomain, LoadErrorReason
 from buildstream.plugintestutils.runcli import cli  # pylint: disable=unused-import
 
-DATA_DIR = os.path.dirname(os.path.realpath(__file__))
-
-
-@contextmanager
-def override_uname_os(name):
-    orig_uname = os.uname
-    orig_tuple = tuple(os.uname())
-    override_result = (name, orig_tuple[1],
-                       orig_tuple[2], orig_tuple[3],
-                       orig_tuple[4])
+from tests.testutils import override_os_uname
 
-    def override():
-        return override_result
-
-    os.uname = override
-    yield
-    os.uname = orig_uname
+DATA_DIR = os.path.dirname(os.path.realpath(__file__))
 
 
 @pytest.mark.datafiles(DATA_DIR)
-@pytest.mark.parametrize("uname,value,expected", [
+@pytest.mark.parametrize("system,value,expected", [
     # Test explicitly provided arches
     ('Darwin', 'Linux', 'Linuxy'),
     ('SunOS', 'FreeBSD', 'FreeBSDy'),
@@ -44,8 +29,8 @@ def override_uname_os(name):
     ('AIX', 'Linux', 'Linuxy'),
     ('HaikuOS', 'SunOS', 'SunOSy'),
 ])
-def test_conditionals(cli, datafiles, uname, value, expected):
-    with override_uname_os(uname):
+def test_conditionals(cli, datafiles, system, value, expected):
+    with override_os_uname(system=system):
         project = os.path.join(datafiles.dirname, datafiles.basename, 'option-os')
 
         bst_args = []
@@ -68,7 +53,7 @@ def test_conditionals(cli, datafiles, uname, value, expected):
 @pytest.mark.datafiles(DATA_DIR)
 def test_unsupported_arch(cli, datafiles):
 
-    with override_uname_os("AIX"):
+    with override_os_uname(system="AIX"):
         project = os.path.join(datafiles.dirname, datafiles.basename, 'option-os')
         result = cli.run(project=project, silent=True, args=[
             'show',
diff --git a/tests/testutils/__init__.py b/tests/testutils/__init__.py
index 67378c959..31912fed9 100644
--- a/tests/testutils/__init__.py
+++ b/tests/testutils/__init__.py
@@ -30,3 +30,4 @@ from .junction import generate_junction
 from .runner_integration import wait_for_cache_granularity
 from .python_repo import setup_pypi_repo
 from .yaml import yaml_file_get_provenance
+from .platform import override_os_uname
diff --git a/tests/testutils/platform.py b/tests/testutils/platform.py
new file mode 100644
index 000000000..e00a131bd
--- /dev/null
+++ b/tests/testutils/platform.py
@@ -0,0 +1,51 @@
+#
+#  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/>.
+#
+#  Authors:
+#        Angelos Evripiotis <jevripiotis@bloomberg.net>
+
+from contextlib import contextmanager
+import os
+
+
+# override_platform_uname()
+#
+# Context manager to override the reported value of `os.uname()`.
+#
+# Args:
+#   system (str): Optional str to replace the 1st entry of uname with.
+#   machine (str): Optional str to replace the 5th entry of uname with.
+#
+@contextmanager
+def override_os_uname(*, system=None, machine=None):
+    orig_func = os.uname
+    result = orig_func()
+
+    result = list(result)
+    if system is not None:
+        result[0] = system
+    if machine is not None:
+        result[4] = machine
+    result = tuple(result)
+
+    def override_func():
+        return result
+
+    os.uname = override_func
+    try:
+        yield
+    finally:
+        os.uname = orig_func