Make TestBase less stateful.

This fixes zipimporter issues noted in pantsbuild#6282 and is generally desirable
in the absence of severe performance degradation.

Fixes pantsbuild#6282

tests/python/pants_test/backend/jvm/tasks/test_check_published_deps.py

@@ -17,11 +17,17 @@
 from pants.build_graph.build_file_aliases import BuildFileAliases
 from pants.build_graph.target import Target
 from pants.java.jar.jar_dependency import JarDependency
+from pants.util.dirutil import safe_mkdir, safe_mkdtemp, safe_open
+from pants.util.memo import memoized_classproperty
 from pants_test.task_test_base import ConsoleTaskTestBase
 
 
 class CheckPublishedDepsTest(ConsoleTaskTestBase):
 
+  @memoized_classproperty
+  def push_db_basedir(cls):
+    return safe_mkdtemp()
+
   @classmethod
   def alias_groups(cls):
     return BuildFileAliases(
@@ -35,10 +41,13 @@ def alias_groups(cls):
         'jar': JarDependency,
         'scala_artifact': ScalaArtifact,
         'scala_jar': ScalaJarDependency,
-        'repo': Repository(name='repo',
-                           url='http://www.www.com',
-                           push_db_basedir=os.path.join(cls._build_root(), 'repo')),
-      }
+
+      },
+      context_aware_object_factories={
+        'repo': lambda _: Repository(name='repo',
+                                     url='http://www.www.com',
+                                     push_db_basedir=cls.push_db_basedir),
+      },
     )
 
   @classmethod
@@ -53,13 +62,19 @@ def assert_console_output(self, *args, **kwargs):
   def setUp(self):
     super(CheckPublishedDepsTest, self).setUp()
 
-    self.create_file('repo/org.name/lib1/publish.properties', dedent("""
+    safe_mkdir(self.push_db_basedir, clean=True)
+
+    def write_db_file(relpath, contents):
+      with safe_open(os.path.join(self.push_db_basedir, relpath), 'w') as fp:
+        fp.write(contents)
+
+    write_db_file('org.name/lib1/publish.properties', dedent("""
         revision.major.org.name%lib1=2
         revision.minor.org.name%lib1=0
         revision.patch.org.name%lib1=0
         revision.sha.org.name%lib1=12345
         """))
-    self.create_file('repo/org.name/lib2/publish.properties', dedent("""
+    write_db_file('org.name/lib2/publish.properties', dedent("""
         revision.major.org.name%lib2=2
         revision.minor.org.name%lib2=0
         revision.patch.org.name%lib2=0

tests/python/pants_test/backend/jvm/tasks/test_jar_publish.py

@@ -4,7 +4,6 @@
 
 from __future__ import absolute_import, division, print_function, unicode_literals
 
-import os
 import unittest
 from builtins import object, str
 
@@ -21,7 +20,8 @@
 from pants.build_graph.target import Target
 from pants.scm.scm import Scm
 from pants.util.contextutil import temporary_dir
-from pants.util.dirutil import safe_mkdir, safe_walk
+from pants.util.dirutil import safe_mkdir, safe_mkdtemp, safe_walk
+from pants.util.memo import memoized_classproperty
 from pants_test.task_test_base import TaskTestBase
 
 
@@ -37,11 +37,12 @@ def test_smoke_publish(self):
       task = self.create_task(self.context())
       task.execute()
 
+  @memoized_classproperty
+  def push_db_basedir(cls):
+    return safe_mkdtemp()
+
   @classmethod
   def alias_groups(cls):
-    cls.push_db_basedir = os.path.join(cls._build_root(), "pushdb")
-    safe_mkdir(cls.push_db_basedir)
-
     return BuildFileAliases(
       targets={
         'jar_library': JarLibrary,
@@ -51,11 +52,18 @@ def alias_groups(cls):
       objects={
         'artifact': Artifact,
         'scala_artifact': ScalaArtifact,
-        'internal': Repository(name='internal', url='http://example.com',
-                               push_db_basedir=cls.push_db_basedir),
+      },
+      context_aware_object_factories={
+        'internal': lambda _: Repository(name='internal',
+                                         url='http://example.com',
+                                         push_db_basedir=cls.push_db_basedir),
       },
     )
 
+  def setUp(self):
+    super(JarPublishTest, self).setUp()
+    safe_mkdir(self.push_db_basedir, clean=True)
+
   def _prepare_for_publishing(self, with_alias=False):
     targets = []
     nail_target = self._create_nail_target()

tests/python/pants_test/test_base.py

@@ -346,21 +346,19 @@ def _reset_engine(self):
       self._build_graph.reset()
       self._scheduler.invalidate_all_files()
 
-  @classmethod
-  def aggressively_reset_scheduler(cls):
-    cls._scheduler = None
-    if cls._local_store_dir is not None:
-      safe_rmtree(cls._local_store_dir)
+  def aggressively_reset_scheduler(self):
+    self._scheduler = None
+    if self._local_store_dir is not None:
+      safe_rmtree(self._local_store_dir)
 
-  @classmethod
   @contextmanager
-  def isolated_local_store(cls):
-    cls.aggressively_reset_scheduler()
-    cls._init_engine()
+  def isolated_local_store(self):
+    self.aggressively_reset_scheduler()
+    self._init_engine()
     try:
       yield
     finally:
-      cls.aggressively_reset_scheduler()
+      self.aggressively_reset_scheduler()
 
   @property
   def build_root(self):
@@ -370,41 +368,38 @@ def build_root(self):
   def pants_workdir(self):
     return self._pants_workdir()
 
-  @classmethod
   @memoized_method
-  def _build_root(cls):
-    cls.real_build_root = BuildRoot().path
+  def _build_root(self):
+    self.real_build_root = BuildRoot().path
     return os.path.realpath(mkdtemp(suffix='_BUILD_ROOT'))
 
-  @classmethod
   @memoized_method
-  def _pants_workdir(cls):
-    return os.path.join(cls._build_root(), '.pants.d')
+  def _pants_workdir(self):
+    return os.path.join(self._build_root(), '.pants.d')
 
-  @classmethod
-  def _init_engine(cls):
-    if cls._scheduler is not None:
+  def _init_engine(self):
+    if self._scheduler is not None:
       return
 
-    cls._local_store_dir = os.path.realpath(safe_mkdtemp())
-    safe_mkdir(cls._local_store_dir)
+    self._local_store_dir = os.path.realpath(safe_mkdtemp())
+    safe_mkdir(self._local_store_dir)
 
     # NB: This uses the long form of initialization because it needs to directly specify
     # `cls.alias_groups` rather than having them be provided by bootstrap options.
     graph_session = EngineInitializer.setup_legacy_graph_extended(
       pants_ignore_patterns=None,
-      workdir=cls._pants_workdir(),
-      local_store_dir=cls._local_store_dir,
+      workdir=self._pants_workdir(),
+      local_store_dir=self._local_store_dir,
       build_file_imports_behavior='allow',
       native=init_native(),
       options_bootstrapper=OptionsBootstrapper.create(args=['--pants-config-files=[]']),
-      build_configuration=cls.build_config(),
+      build_configuration=self.build_config(),
       build_ignore_patterns=None,
     ).new_session()
-    cls._scheduler = graph_session.scheduler_session
-    cls._build_graph, cls._address_mapper = graph_session.create_build_graph(
-        TargetRoots([]), cls._build_root()
-      )
+    self._scheduler = graph_session.scheduler_session
+    self._build_graph, self._address_mapper = graph_session.create_build_graph(
+      TargetRoots([]), self._build_root()
+    )
 
   @property
   def scheduler(self):