{"id":4422,"library":"anys","title":"Anys: Pytest Matchers","description":"anys provides a collection of matchers designed for pytest-style assertions, enabling more flexible comparisons in unit tests. Instead of strict equality checks, it allows developers to assert that values meet specific criteria (e.g., `ANY_DATETIME_STR` for any valid ISO 8601 timestamp string). This simplifies testing dynamic or partially unpredictable data structures. The library is actively maintained, with the current version being 0.3.1.","status":"active","version":"0.3.1","language":"en","source_language":"en","source_url":"https://github.com/jwodder/anys","tags":["pytest","testing","matchers","assertion","unit testing","flexible comparison"],"install":[{"cmd":"pip install anys","lang":"bash","label":"Install with pip"}],"dependencies":[{"reason":"Requires Python 3.8 or higher for compatibility.","package":"python","optional":false}],"imports":[{"symbol":"ANY_DATETIME_STR","correct":"from anys import ANY_DATETIME_STR"},{"symbol":"ANY_INT","correct":"from anys import ANY_INT"},{"symbol":"ANY_STR","correct":"from anys import ANY_STR"},{"symbol":"AnyGT","correct":"from anys import AnyGT"},{"symbol":"AnyLT","correct":"from anys import AnyLT"},{"note":"While technically possible, the documentation examples primarily use direct `from anys import ...` for brevity and clarity when using specific matchers.","wrong":"import anys; assert foo == anys.AnyMatch(...)","symbol":"AnyMatch","correct":"from anys import AnyMatch"}],"quickstart":{"code":"from anys import ANY_DATETIME_STR\n\ndef test_api_response():\n    # Imagine this is a dynamic response from an API or function\n    dynamic_data = {\n        \"id\": \"user-123\",\n        \"name\": \"Test User\",\n        \"created_at\": \"2024-04-12T10:30:00Z\",\n        \"details\": {\n            \"status\": \"active\",\n            \"last_login\": \"2024-04-12T10:29:55Z\"\n        }\n    }\n\n    # Assert against a structure with matchers for dynamic fields\n    expected_pattern = {\n        \"id\": ANY_STR, # Match any string\n        \"name\": \"Test User\",\n        \"created_at\": ANY_DATETIME_STR, # Match any valid ISO datetime string\n        \"details\": {\n            \"status\": ANY_STR,\n            \"last_login\": ANY_DATETIME_STR\n        }\n    }\n\n    assert dynamic_data == expected_pattern\n    print(\"Assertion successful: Dynamic data matches expected pattern!\")\n\ntest_api_response()","lang":"python","description":"This quickstart demonstrates how to use `anys` for flexible assertions, particularly with dynamic data like API responses. It uses `ANY_STR` to match any string and `ANY_DATETIME_STR` to match any valid ISO 8601 datetime string, allowing the test to pass even if the exact values for `id`, `created_at`, `status`, or `last_login` are not known in advance."},"warnings":[{"fix":"Be explicit about the expected types when using matchers. If a type mismatch might be indicative of a bug, consider adding a separate `isinstance()` check or use matchers specifically designed for numeric types (e.g., `ANY_INT`, `AnyGT`).","message":"When an `anys` matcher encounters a `TypeError` or `ValueError` during comparison (e.g., attempting to apply a regular expression matcher like `AnyMatch(r'\\d+')` to an integer `42`), the library explicitly suppresses the exception and the comparison silently evaluates to `False`. This behavior, while intended, can mask unexpected type mismatches that might indicate a deeper issue if not anticipated.","severity":"gotcha","affected_versions":"All versions"},{"fix":"Consult the `anys` documentation for each specific matcher to understand what types of arguments it accepts. For complex nested matching, ensure each level of matching is compatible with the parent matcher's design.","message":"Most `anys` class constructors (e.g., `AnyHas`, `AnyMapping`, `AnyDictOf`) are not designed to take other `anys` matchers as arguments for their keys or specific internal structures unless explicitly documented. Attempting to nest matchers in unsupported ways may lead to unexpected comparison results, `False` evaluations due to suppressed errors, or incorrect behavior.","severity":"gotcha","affected_versions":"All versions"}],"env_vars":null,"last_verified":"2026-04-12T00:00:00.000Z","next_check":"2026-07-11T00:00:00.000Z"}