Memory leak and high CPU after stepping over mocker.patch("time.sleep") from pytest-mock

[freetomik]

Type: Performance Issue

1. with following Python code and installed packages pytest and pytest-mock:

import time

def test_sleep_with_mock(mocker):
    mocker.patch("time.sleep")
    time.sleep(5)
    time.sleep.assert_called_once_with(5)

2. set breakpoint on line with mocker.patch(...)
3. start test debugging (via Testing icon on Activity Bar)
4. step over the line (F10)

• expected behaviour:
  CPU and memory stay and same level like before stepping over the line. On Continue (F5) test finishes.

• actual behaviour:
  CPU goes from 5% to 25% and memory starts to gradually increase. On Continue (F5) test hangs.

Windows 10 Pro 22H2 19045.4046, x64
Python 3.12.6
pytest==8.1.2
pytest-mock==3.14.0

VS Code version: Code 1.93.1 (38c31bc77e0dd6ae88a4e9cc93428cc27a56ba40, 2024-09-11T17:20:05.685Z)
OS version: Windows_NT x64 10.0.19045
Modes:

System Info

Item	Value
CPUs	11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz (8 x 2803)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: enabled_on direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: disabled_off video_decode: enabled video_encode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	undefined
Memory (System)	15.69GB (4.14GB free)
Process Argv	--crash-reporter-id dfe8ae6d-b221-4f14-9a09-388238534166
Screen Reader	no
VM	0%

Process Info

CPU %	Mem MB	   PID	Process
    0	   120	 43112	code main
    0	   182	  9060	   gpu-process
    0	    43	 25048	   utility-network-service
    0	    27	 26756	   crashpad-handler
    0	   273	 27592	window [1] (test_sleep2.py - pytest-mock-example - Visual Studio Code)
    0	   109	 38540	shared-process
    0	    88	 42892	fileWatcher [1]
    0	   432	 44828	extensionHost [1]
    0	   361	  4680	     electron-nodejs (bundle.js )
    0	     7	 37708	     c:\Users\<user>\.vscode\extensions\ms-python.python-2024.14.1-win32-x64\python-env-tools\bin\pet.exe server
    0	    11	 13304	       C:\windows\system32\conhost.exe 0x4
    0	     4	 41544	     "c:\Users\<user>\Documents\Python skripty\pytest-mock-example\.venv\Scripts\python.exe" c:\Users\<user>\.vscode\extensions\ms-python.isort-2023.10.1\bundled\tool\lsp_server.py
    0	    48	 38556	       "C:\Users\<user>\AppData\Local\Programs\Python\Python312\python.exe" c:\Users\<user>\.vscode\extensions\ms-python.isort-2023.10.1\bundled\tool\lsp_server.py
    0	    11	 41000	       C:\windows\system32\conhost.exe 0x4
    0	   113	 45968	ptyHost
    0	   100	  3856	     "C:\Program Files\PowerShell\7\pwsh.exe" -noexit -command "try { . \"c:\Users\<user>\AppData\Local\Programs\Microsoft VS Code\resources\app\out\vs\workbench\contrib\terminal\browser\media\shellIntegration.ps1\" } catch {}"
    0	     6	  6500	     conpty-agent
    0	     6	 15724	     conpty-agent
    0	   108	 22500	     "C:\Program Files\PowerShell\7\pwsh.exe" -noexit -command "try { . \"c:\Users\<user>\AppData\Local\Programs\Microsoft VS Code\resources\app\out\vs\workbench\contrib\terminal\browser\media\shellIntegration.ps1\" } catch {}"
    0	   100	 22820	     "C:\Program Files\PowerShell\7\pwsh.exe" -noexit -command "try { . \"c:\Users\<user>\AppData\Local\Programs\Microsoft VS Code\resources\app\out\vs\workbench\contrib\terminal\browser\media\shellIntegration.ps1\" } catch {}"
    0	    96	 30528	     "C:\Program Files\PowerShell\7\pwsh.exe" -noexit -command "try { . \"c:\Users\<user>\AppData\Local\Programs\Microsoft VS Code\resources\app\out\vs\workbench\contrib\terminal\browser\media\shellIntegration.ps1\" } catch {}"
    0	    99	 36596	     "C:\Program Files\PowerShell\7\pwsh.exe" -noexit -command "try { . \"c:\Users\<user>\AppData\Local\Programs\Microsoft VS Code\resources\app\out\vs\workbench\contrib\terminal\browser\media\shellIntegration.ps1\" } catch {}"
    0	     6	 42568	     conpty-agent
    0	     7	 42752	     conpty-agent
    0	     6	 45608	     conpty-agent

Workspace Info

|  Window (test_sleep2.py - pytest-mock-example - Visual Studio Code)
|    Folder (pytest-mock-example): 8310 files
|      File types: pyc(2233) py(2231) gz(1052) json(870) txt(40) pyi(36)
|                  typed(27) exe(16) pyd(6) md(5)
|      Conf files: settings.json(1);

Extensions (26)

Extension	Author (truncated)	Version
cucumberautocomplete	ale	3.0.5
vscode-log-viewer	ber	0.14.1
json-tools	eri	1.0.2
prettier-vscode	esb	11.0.0
copilot	Git	1.231.1112
copilot-chat	Git	0.20.2
rainbow-csv	mec	3.12.0
playwright	ms-	1.1.7
debugpy	ms-	2024.10.0
isort	ms-	2023.10.1
python	ms-	2024.14.1
vscode-pylance	ms-	2024.9.1
jupyter	ms-	2024.8.1
jupyter-keymap	ms-	1.1.2
jupyter-renderers	ms-	1.0.19
vscode-jupyter-cell-tags	ms-	0.1.9
vscode-jupyter-slideshow	ms-	0.1.6
powershell	ms-	2024.2.2
vscode-speech	ms-	0.10.0
vsliveshare	ms-	1.0.5940
playwright-test-snippets	msk	1.2.1
LiveServer	rit	5.7.9
markdown-preview-enhanced	shd	0.8.14
german-scroll	Tur	0.2.3
vim	vsc	1.28.1
JavaScriptSnippets	xab	1.8.0

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welcomedialog:30910333
pythonnoceb:30805159
asynctok:30898717
pythonmypyd1:30879173
h48ei257:31000450
pythontbext0:30879054
accentitlementsc:30995553
dsvsc016:30899300
dsvsc017:30899301
dsvsc018:30899302
cppperfnew:31000557
dsvsc020:30976470
pythonait:31006305
dsvsc021:30996838
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dvdeprecation:31068756
dwnewjupytercf:31046870
impr_priority:31102340
nativerepl1:31139838
refactort:31108082
pythonrstrctxt:31112756
flighttreat:31134774
wkspc-onlycs-t:31132770
wkspc-ranged-t:31125599
cf971741:31134768
pme_test_c:31118331
fje88620:31121564
iacca1:31138162

[rchiodo]

I see no such spike in CPU or memory usage. This might have been an issue with the 3.12 debugger that was fixed in the October timeframe.