[PATCH 06/22] tests/functional: introduce some helpful decorators

["Daniel P. Berrangé" <berrange@redhat.com>]

Reduce repeated boilerplate with some helper decorators:

 @skipIfNotPlatform("x86_64", "aarch64")

  => Skip unless the build host platform matches

 @skipIfMissingCommands("mkisofs", "losetup")

  => Skips unless all listed commands are found in $PATH

 @skipIfMissingImports("numpy", "cv2")

  => Skips unless all listed modules can be imported

 @skipFlakyTest("https://gitlab.com/qemu-project/qemu/-/issues/NNN")

  => Skips unless env var requests flaky tests with the
     reason documented in the referenced gitlab bug

 @skipBigData

  => Skips unless env var permits tests creating big data files

 @skipUntrustedTest

  => Skips unless env var permits tests which are potentially
     dangerous to the host

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 tests/functional/qemu_test/__init__.py   |   3 +
 tests/functional/qemu_test/decorators.py | 105 +++++++++++++++++++++++
 2 files changed, 108 insertions(+)
 create mode 100644 tests/functional/qemu_test/decorators.py

diff --git a/tests/functional/qemu_test/__init__.py b/tests/functional/qemu_test/__init__.py
index 8fddddbe67..7dee3522f2 100644
--- a/tests/functional/qemu_test/__init__.py
+++ b/tests/functional/qemu_test/__init__.py
@@ -13,3 +13,6 @@
     exec_command, exec_command_and_wait_for_pattern, get_qemu_img, which
 from .testcase import QemuBaseTest, QemuUserTest, QemuSystemTest
 from .linuxkernel import LinuxKernelTest
+from .decorators import skipIfMissingCommands, skipIfNotMachine, \
+    skipFlakyTest, skipUntrustedTest, skipBigDataTest, \
+    skipIfMissingImports
diff --git a/tests/functional/qemu_test/decorators.py b/tests/functional/qemu_test/decorators.py
new file mode 100644
index 0000000000..d25fec7b2d
--- /dev/null
+++ b/tests/functional/qemu_test/decorators.py
@@ -0,0 +1,105 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# Decorators useful in functional tests
+
+import os
+import platform
+from unittest import skipUnless
+
+from .cmd import which
+
+'''
+Decorator to skip execution of a test if the list
+of command binaries is not available in $PATH.
+Example:
+
+  @skipIfMissingCommands("mkisofs", "losetup")
+'''
+def skipIfMissingCommands(*args):
+    def has_cmds(cmdlist):
+        for cmd in cmdlist:
+            if not which(cmd):
+                return False
+        return True
+
+    return skipUnless(lambda: has_cmds(args),
+                      'required commands(s) "%s" not installed' %
+                      ", ".join(args))
+
+'''
+Decorator to skip execution of a test if the current
+host machine does not match one of the permitted
+machines.
+Example
+
+  @skipIfNotMachine("x86_64", "aarch64")
+'''
+def skipIfNotMachine(*args):
+    return skipUnless(lambda: platform.machine() in args,
+                        'not running on required machine(s) "%s"' %
+                        ", ".join(args))
+
+'''
+Decorator to skip execution of flaky tests, unless
+the $QEMU_TEST_FLAKY_TESTS env var is set. A bug URL
+must be provided that documents the observed failure
+behaviour, so it can be tracked & re-evaluated in future.
+
+Historical tests may be providing "None" as the bug_url
+but this should not be done for new test.
+
+Example:
+
+  @skipFlakyTest("https://gitlab.com/qemu-project/qemu/-/issues/NNN")
+'''
+def skipFlakyTest(bug_url):
+    if bug_url is None:
+        bug_url = "FIXME: reproduce flaky test and file bug report or remove"
+    return skipUnless(os.getenv('QEMU_TEST_FLAKY_TESTS'),
+                      f'Test is unstable: {bug_url}')
+
+'''
+Decorator to skip execution of tests which are likely
+to execute untrusted commands on the host, or commands
+which process untrusted code, unles the
+$QEMU_TEST_ALLOW_UNTRUSTED_CODE env var is set.
+Example:
+
+  @skipUntrustedTest()
+'''
+def skipUntrustedTest():
+    return skipUnless(os.getenv('QEMU_TEST_ALLOW_UNTRUSTED_CODE'),
+                      'Test runs untrusted code / processes untrusted data')
+
+'''
+Decorator to skip execution of tests which need large
+data storage on the host, unless the
+$QEMU_TEST_ALLOW_LARGE_STORAGE env var is set
+
+Example:
+
+  @skipBigDataTest()
+'''
+def skipBigDataTest():
+    return skipUnless(os.getenv('QEMU_TEST_ALLOW_LARGE_STORAGE'),
+                      'Test required large host storage space')
+
+'''
+Decorator to skip execution of a test if the list
+of python imports is not available.
+Example:
+
+  @skipIfMissingImports("numpy", "cv2")
+'''
+def skipIfMissingImports(*args):
+    def has_imports(importlist):
+        for impname in importlist:
+            try:
+                import impname
+            except ImportError:
+                return False
+        return True
+
+    return skipUnless(lambda: has_imports(args),
+                      'required imports(s) "%s" not installed' %
+                      ", ".join(args))
-- 
2.46.0