AssertPy

Warnings

• breaking The `assert_soft()` function was renamed to `assert_warn()`.
  Fix: Update calls from `assert_soft()` to `assert_warn()`.
• breaking The `extract()` helper function was renamed to `extracting()`.
  Fix: Change all uses of `extract()` to `extracting()`.
• gotcha Older versions of AssertPy supported Python 2.x, but modern versions are Python 3.x only. Specific older Python 3 versions (e.g., 3.3, 2.6) have also been dropped over time.
  Fix: Ensure you are using a Python 3 environment (Python 3.4-3.8 for v1.1) for full compatibility. Check `assertpy`'s PyPI classifiers for specific version support.
• gotcha When using `matches()` for regular expression assertions, be aware that it performs a partial match (like `re.match`). For exact full string matches, include anchors (e.g., `^...$`) in your regex pattern.
  Fix: Use raw strings (`r'pattern'`) for regex patterns and include `^` and `$` anchors for full string matching if desired.
• gotcha For `dict` equality comparisons with `is_equal_to()`, you can control which keys are included or ignored. If not specified, all keys are compared.
  Fix: Utilize the `include` (or `ignore`) keyword argument in `is_equal_to(expected_dict, include=['key1', 'key2'])` for precise dict comparisons.
• gotcha Snapshot testing (`.snapshot()`) requires Python 3.x and saves artifacts to disk (e.g., `__snapshots` directory by default). These artifacts should be committed to version control.
  Fix: Ensure Python 3 is used for snapshot tests and add the `__snapshots` directory (or custom path) to your version control.

Install

• pip install assertpy Install latest version

Imports

• assert_that

  from assertpy import assert_that

  The primary entry point for all fluent assertions.
• soft_assertions

  from assertpy import soft_assertions

  Used as a context manager to collect multiple assertion failures without halting execution immediately.
• assert_warn

  from assertpy import assert_warn

  Renamed from `assert_soft` in v0.10; logs warnings instead of raising an AssertionError.

Quickstart

This quickstart demonstrates basic chained assertions using `assert_that` and shows how to use `soft_assertions` as a context manager to collect multiple failures before raising a single `AssertionError` at the end of the block.

from assertpy import assert_that, soft_assertions

def test_basic_assertions():
    assert_that(1 + 2).is_equal_to(3)
    assert_that('foobar').is_length(6).starts_with('foo').ends_with('bar')
    assert_that(['a', 'b', 'c']).contains('a').does_not_contain('x')
    print('Basic assertions passed.')

def test_soft_assertions():
    with soft_assertions():
        assert_that(1).is_equal_to(2)  # This will fail
        assert_that('hello').is_length(10) # This will also fail
    print('Soft assertions completed. Failures (if any) are collected.')

test_basic_assertions()
test_soft_assertions()