From f0a0d6d0771f5bd8b1df8e5a8d2b8991870533a5 Mon Sep 17 00:00:00 2001
From: Giampaolo Rodola <g.rodola@gmail.com>
Date: Thu, 15 Dec 2022 21:42:36 +0100
Subject: write extensive test suite for @memoize decorator

---
 Makefile                  |   6 +--
 psutil/_common.py         |   9 ++++
 psutil/tests/test_misc.py | 106 +++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 114 insertions(+), 7 deletions(-)

diff --git a/Makefile b/Makefile
index 5088cb72..c27db46d 100644
--- a/Makefile
+++ b/Makefile
@@ -121,7 +121,7 @@ setup-dev-env:  ## Install GIT hooks, pip, test deps (also upgrades them).
 # Tests
 # ===================================================================
 
-test:  ## Run all tests.
+test:  ## Run all tests. To run a specific test do "make test ARGS=psutil.tests.test_system.TestDiskAPIs"
 	${MAKE} build
 	$(TEST_PREFIX) $(PYTHON) $(TSCRIPT) $(ARGS)
 
@@ -169,10 +169,6 @@ test-memleaks:  ## Memory leak tests.
 	${MAKE} build
 	$(TEST_PREFIX) $(PYTHON) $(TSCRIPT) $(ARGS) psutil/tests/test_memleaks.py
 
-test-by-name:  ## e.g. make test-by-name ARGS=psutil.tests.test_system.TestSystemAPIs
-	${MAKE} build
-	$(TEST_PREFIX) $(PYTHON) $(TSCRIPT) $(ARGS)
-
 test-failed:  ## Re-run tests which failed on last run
 	${MAKE} build
 	$(TEST_PREFIX) $(PYTHON) $(TSCRIPT) $(ARGS) --last-failed
diff --git a/psutil/_common.py b/psutil/_common.py
index 3414e8ca..387d9594 100644
--- a/psutil/_common.py
+++ b/psutil/_common.py
@@ -391,6 +391,15 @@ def memoize(fun):
     1
     >>> foo.cache_clear()
     >>>
+
+    It supports:
+     - functions
+     - classes (acts as a @singleton)
+     - staticmethods
+     - classmethods
+
+    It does NOT support:
+     - methods
     """
     @functools.wraps(fun)
     def wrapper(*args, **kwargs):
diff --git a/psutil/tests/test_misc.py b/psutil/tests/test_misc.py
index e22789c1..1ff0f52f 100755
--- a/psutil/tests/test_misc.py
+++ b/psutil/tests/test_misc.py
@@ -291,9 +291,108 @@ class TestMisc(PsutilTestCase):
 # ===================================================================
 
 
-class TestCommonModule(PsutilTestCase):
+class TestMemoizeDecorator(PsutilTestCase):
+
+    def setUp(self):
+        self.calls = []
+
+    tearDown = setUp
+
+    def run_against(self, obj, expected_retval=None):
+        # no args
+        for x in range(2):
+            ret = obj()
+            self.assertEqual(self.calls, [((), {})])
+            if expected_retval is not None:
+                self.assertEqual(ret, expected_retval)
+        # with args
+        for x in range(2):
+            ret = obj(1)
+            self.assertEqual(self.calls, [((), {}), ((1, ), {})])
+            if expected_retval is not None:
+                self.assertEqual(ret, expected_retval)
+        # with args + kwargs
+        for x in range(2):
+            ret = obj(1, bar=2)
+            self.assertEqual(
+                self.calls, [((), {}), ((1, ), {}), ((1, ), {'bar': 2})])
+            if expected_retval is not None:
+                self.assertEqual(ret, expected_retval)
+        # clear cache
+        self.assertEqual(len(self.calls), 3)
+        obj.cache_clear()
+        ret = obj()
+        if expected_retval is not None:
+            self.assertEqual(ret, expected_retval)
+        self.assertEqual(len(self.calls), 4)
+        # docstring
+        self.assertEqual(obj.__doc__, "my docstring")
 
-    def test_memoize(self):
+    def test_function(self):
+        @memoize
+        def foo(*args, **kwargs):
+            """my docstring"""
+            baseclass.calls.append((args, kwargs))
+            return 22
+
+        baseclass = self
+        self.run_against(foo, expected_retval=22)
+
+    def test_class(self):
+        @memoize
+        class Foo:
+            """my docstring"""
+
+            def __init__(self, *args, **kwargs):
+                baseclass.calls.append((args, kwargs))
+
+            def bar(self):
+                return 22
+
+        baseclass = self
+        self.run_against(Foo, expected_retval=None)
+        self.assertEqual(Foo().bar(), 22)
+
+    def test_class_singleton(self):
+        # @memoize can be used against classes to create singletons
+        @memoize
+        class Bar:
+            def __init__(self, *args, **kwargs):
+                pass
+
+        self.assertIs(Bar(), Bar())
+        self.assertEqual(id(Bar()), id(Bar()))
+        self.assertEqual(id(Bar(1)), id(Bar(1)))
+        self.assertEqual(id(Bar(1, foo=3)), id(Bar(1, foo=3)))
+        self.assertNotEqual(id(Bar(1)), id(Bar(2)))
+
+    def test_staticmethod(self):
+        class Foo:
+            @staticmethod
+            @memoize
+            def bar(*args, **kwargs):
+                """my docstring"""
+                baseclass.calls.append((args, kwargs))
+                return 22
+
+        baseclass = self
+        self.run_against(Foo().bar, expected_retval=22)
+
+    def test_classmethod(self):
+        class Foo:
+            @classmethod
+            @memoize
+            def bar(cls, *args, **kwargs):
+                """my docstring"""
+                baseclass.calls.append((args, kwargs))
+                return 22
+
+        baseclass = self
+        self.run_against(Foo().bar, expected_retval=22)
+
+    def test_original(self):
+        # This was the original test before I made it dynamic to test it
+        # against different types. Keeping it anyway.
         @memoize
         def foo(*args, **kwargs):
             """foo docstring"""
@@ -328,6 +427,9 @@ class TestCommonModule(PsutilTestCase):
         # docstring
         self.assertEqual(foo.__doc__, "foo docstring")
 
+
+class TestCommonModule(PsutilTestCase):
+
     def test_memoize_when_activated(self):
         class Foo:
 
-- 
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