PyNose: a Test Smell Detector for Python

PyNose is a test smell detector tool for Python. It runs as a plugin inside the PyCharm IDE (version 2021.3)

Note: PyNose is currently under active development, the older version of the tool that was initially described in the paper "PyNose: A Test Smell Detector For Python" can be found in the ASE2021 branch.

How to use in PyCharm

1. Download the latest release of the plugin from here;
2. Open PyCharm and go to File/Settings/Plugins;
3. Select the gear icon, and choose Install Plugin from Disk...;
4. Choose the downloaded ZIP archive;
5. Click Apply;
6. Restart the IDE.

Description

PyNose can be used inside the IDE to study the test smells within a specific opened project. This can help python developers avoid test smells in their code.

When you open a project in PyCharm, a number of inspections will be available for usage.

PyNose will retrieve the information about your currently configured Test Runner (Preferences > Tools > Python Integrated Tools > Testing > Default test runner) to use the appropriate set of inspections (pytest or Unittest).

Some inspections are initially disabled, however you can enable them from the settings.

Available inspections

Inspections	Unittest	Pytest	Quick fix	Warning level	Description
Assertion Roulette	+	+	-	Disabled*	A test case contains more than one assertion statement without an explanation
Conditional Test Logic	+	+	-	Disabled	Presence of control statements (i.e., if, for, while)
Constructor Initialization	+	-	+ (move logic to setup)	Weak warning	A test suite contains a constructor declaration (an __init__ method)
Default Test	+	-	+ (suggest rename refactoring)	Weak warning	A test suite is called MyTestCase
Duplicate Assert	+	+	+ (remove duplicate)	Warning	Occurrence of more than one assertion statement with the same parameters
Empty Test	+	+	+ (safe delete)	Warning	A test case does not contain a single executable statement
Exception Handling	+	+	+ (replace with framework raise handler)	Warning	Presence of either the try/except statement or the raise statement
Lack of Cohesion of Test Cases	+	+	-	Disabled	Test suites in a test case are not cohesive according to pairwise cosine similarities metric
Magic Number Test	+	+	-	Disabled	Presence of an assertion statement with a numeric literal as an argument
Obscure In-Line Setup	+	+	-	Disabled	A test case contains ten or more local variables declarations
Redundant Assertion	+	+	+ (remove assertion)	Warning	Presence of assertions the result of which never changes (i.e., assert 1 == 1)
Redundant Print	+	+	+ (remove statement)	Disabled	print() function invocation
Sleepy Test	+	+	+ (remove statement)	Disabled	time.sleep() function invocation
Suboptimal Assert	+	-	+ (replace with optimal)	Warning	Presence of one of the suboptimal asserts**
Test Maverick	+	+	-	Disabled	A test suite contains at least one test case that does not use a single field from the setup method

*Disabled by default. If enabled — weak warning.

**List of suboptimal assertions is available here.

Usage examples

• Suboptimal assertion detection and quick fix
  
  
  
  

• Exception handling detection and quick fix
  
  
  
  

Contacts

If you have any questions or suggestions, don't hesitate to open an issue or contact Yaroslav Golubev at yaroslav.golubev@jetbrains.com.