# pytest-check

A pytest plugin that allows multiple failures per test.

----

Normally, a test function will fail and stop running with the first failed `assert`.
That's totally fine for tons of kinds of software tests.
However, there are times where you'd like to check more than one thing, and you'd really like to know the results of each check, even if one of them fails.

`pytest-check` allows multiple failed "checks" per test function, so you can see the whole picture of what's going wrong.

## Installation

From PyPI:

```
$ pip install pytest-check
```

From conda (conda-forge):
```
$ conda install -c conda-forge pytest-check
```

## Example

Quick example of where you might want multiple checks:

```python
import httpx
from pytest_check import check

def test_httpx_get():
    r = httpx.get('https://www.example.org/')
    # bail if bad status code
    assert r.status_code == 200
    # but if we get to here
    # then check everything else without stopping
    with check:
        assert r.is_redirect is False
    with check:
        assert r.encoding == 'utf-8'
    with check:
        assert 'Example Domain' in r.text
```

## Import vs fixture

The example above used import: `from pytest_check import check`.

You can also grab `check` as a fixture with no import:

```python
def test_httpx_get(check):
    r = httpx.get('https://www.example.org/')
    ...
    with check:
        assert r.is_redirect == False
    ...
```

## Validation functions

`check` also helper functions for common checks. 
These methods do NOT need to be inside of a `with check:` block.

| Function    | Meaning    | Notes    |
|------------------------------------------------------|-----------------------------------|------------------------------------------------------------------------------------------------------|
| `equal(a, b, msg="")`    | `a == b`    |    |
| `not_equal(a, b, msg="")`    | `a != b`    |    |
| `is_(a, b, msg="")`    | `a is b`    |    |
| `is_not(a, b, msg="")`    | `a is not b`    |    |
| `is_true(x, msg="")`    | `bool(x) is True`    |    |
| `is_false(x, msg="")`    | `bool(x) is False`    |    |
| `is_none(x, msg="")`    | `x is None`    |    |
| `is_not_none(x, msg="")`    | `x is not None`    |    |
| `is_in(a, b, msg="")`    | `a in b`    |    |
| `is_not_in(a, b, msg="")`    | `a not in b`    |    |
| `is_instance(a, b, msg="")`    | `isinstance(a, b)`    |    |
| `is_not_instance(a, b, msg="")`    | `not isinstance(a, b)`    |    |
| `is_nan(x, msg="")`    | `math.isnan(x)`    | [math.isnan](https://docs.python.org/3/library/math.html#math.isnan)   |
| `is_not_nan(x, msg="")`    | `not math.isnan(x) `    | [math.isnan](https://docs.python.org/3/library/math.html#math.isnan)   | 
| `almost_equal(a, b, rel=None, abs=None, msg="")`    | `a == pytest.approx(b, rel, abs)` | [pytest.approx](https://docs.pytest.org/en/latest/reference.html#pytest-approx)    |
| `not_almost_equal(a, b, rel=None, abs=None, msg="")` | `a != pytest.approx(b, rel, abs)` | [pytest.approx](https://docs.pytest.org/en/latest/reference.html#pytest-approx)    | 
| `greater(a, b, msg="")`    | `a > b`    |    |
| `greater_equal(a, b, msg="")`    | `a >= b`    |    |
| `less(a, b, msg="")`    | `a < b`    |    |
| `less_equal(a, b, msg="")`    | `a <= b`    |    |
| `between(b, a, c, msg="", ge=False, le=False)`    | `a < b < c`    |    |
| `between_equal(b, a, c, msg="")`    | `a <= b <= c`    | same as `between(b, a, c, msg, ge=True, le=True)`    |
| `raises(expected_exception, *args, **kwargs)`    | *Raises given exception*    | similar to [pytest.raises](https://docs.pytest.org/en/latest/reference/reference.html#pytest-raises) | 
| `fail(msg)`    | *Log a failure*    |    |

**Note: This is a list of relatively common logic operators. I'm reluctant to add to the list too much, as it's easy to add your own.**

All built-in check helper functions in this list also accept an optional `xfail` reason, for example:

```python
check.equal(actual, expected, xfail="known issue #123")
```

If that check fails, the test can be reported as xfailed.
If the check passes, this does **not** create an xpass unless the test was already marked with `@pytest.mark.xfail`.


The httpx example can be rewritten with helper functions:

```python
def test_httpx_get_with_helpers():
    r = httpx.get('https://www.example.org/')
    assert r.status_code == 200
    check.is_false(r.is_redirect)
    check.equal(r.encoding, 'utf-8')
    check.is_in('Example Domain', r.text)
```

Which you use is personal preference.

## Defining your own check functions

### Using `@check.check_func`

The `@check.check_func` decorator allows you to wrap any test helper that has an assert statement in it to be a non-blocking assert function.


```python
from pytest_check import check

@check.check_func
def is_four(a):
    assert a == 4

def test_all_four():
    is_four(1)
    is_four(2)
    is_four(3)
    is_four(4)
```

### Built in check functions return bool

The return value of all the check functions that come pre-written in pytest-check return a bool value.  
You can use that to determine if it passes or fails. 

So, if you want to perform some action based on success/failure, you can just do something like:

```python
from pytest_check import check

def test_something()
    ...
    if check.equal(a, b):
        # they are equal
        ...
    else
        # they are not equal
        # and a failure was registered by the check method
        ...
```

### Using `check.fail()`

Using `@check.check_func` is probably the easiest. 
However, it does have a bit of overhead in the passing cases 
that can affect large loops of checks.

If you need a bit of a speedup, use the following style with the help of `check.fail()`.

```python
from pytest_check import check

def is_four(a):
    __tracebackhide__ = True
    if a == 4:
        return True
    else: 
        check.fail(f"check {a} == 4")
        return False

def test_all_four():
  is_four(1)
  is_four(2)
  is_four(3)
  is_four(4)
```

## Using raises as a context manager

`raises` is used as context manager, much like `pytest.raises`. The main difference being that a failure to raise the right exception won't stop the execution of the test method.


```python
from pytest_check import check

def test_raises():
    with check.raises(AssertionError):
        x = 3
        assert 1 < x < 4

def test_raises_exception_value():
    with check.raises(ValueError) as e:
        raise ValueError("This is a ValueError")
    check.equal(str(e.value) == "This is a ValueError")
```

If the exception isn't correct, as in it isn't the exception type raised, the error message reported for the test failure will describe the actual exception.

```python
def test_raises_fail():
    with check.raises(ValueError):
        x = 1 / 0 # division by zero error, NOT ValueError
        assert x == 0
```

If you want a custom message instead, you can supply one.   
Note, this doesn't check that msg matches the exception string.  
It simply is a custom failure message for your test. 

```python
def test_raises_and_custom_fail_message():
    with check.raises(ValueError, msg="custom"):
        x = 1 / 0 # division by zero error, NOT ValueError
        assert x == 0
```

`raises()` also accepts an `xfail` reason.
If the `raises` check fails, the test can be reported as xfailed.
If it passes, this does **not** create an xpass unless the test is already marked with `@pytest.mark.xfail`.

```python
def test_raises_and_xfail():
    with check.raises(ValueError, xfail="known issue #123"):
        x = 1 / 0 # division by zero error, NOT ValueError
        assert x == 0
```


## Pseudo-tracebacks

With `check`, tests can have multiple failures per test.
This would possibly make for extensive output if we include the full traceback for
every failure.
To make the output a little more concise, `pytest-check` implements a shorter version, which we call pseudo-tracebacks. 
And to further make the output more concise, and speed up the test run, only the first pseudo-traceback is turned on by default.

For example, take this test:

```python
def test_example():
    a = 1
    b = 2
    c = [2, 4, 6]
    check.greater(a, b)
    check.less_equal(b, a)
    check.is_in(a, c, "Is 1 in the list")
    check.is_not_in(b, c, "make sure 2 isn't in list")
```

This will result in:

```
$ pytest test_check.py                 
...
================================= FAILURES =================================
_______________________________ test_example _______________________________

FAILURE: check 1 > 2
test_check.py:7 in test_example() -> check.greater(a, b)

FAILURE: check 2 <= 1
FAILURE: check 1 in [2, 4, 6]: Is 1 in the list
FAILURE: check 2 not in [2, 4, 6]: make sure 2 isn't in list
------------------------------------------------------------
Failed Checks: 4
========================= short test summary info ==========================
FAILED test_check.py::test_example - check 1 > 2
============================ 1 failed in 0.01s =============================
```


If you wish to see more pseudo-tracebacks than just the first, you can set `--check-max-tb=5` or something larger:


```
(.venv) $ pytest test_check.py --check-max-tb=5
=========================== test session starts ============================
collected 1 item                                                           

test_check.py F                                                      [100%]

================================= FAILURES =================================
_______________________________ test_example _______________________________

FAILURE: check 1 > 2
test_check.py:7 in test_example() -> check.greater(a, b)

FAILURE: check 2 <= 1
test_check.py:8 in test_example() -> check.less_equal(b, a)

FAILURE: check 1 in [2, 4, 6]: Is 1 in the list
test_check.py:9 in test_example() -> check.is_in(a, c, "Is 1 in the list")

FAILURE: check 2 not in [2, 4, 6]: make sure 2 isn't in list
test_check.py:10 in test_example() -> check.is_not_in(b, c, "make sure 2 isn't in list")

------------------------------------------------------------
Failed Checks: 4
========================= short test summary info ==========================
FAILED test_check.py::test_example - check 1 > 2
============================ 1 failed in 0.01s =============================
```

## Red output

The failures will also be red, unless you turn that off with pytests `--color=no`.

## No output

You can turn off the failure reports with pytests `--tb=no`.

## Stop on Fail (maxfail behavior)

Setting `-x` or `--maxfail=1` will cause this plugin to abort testing after the first failed check.

Setting `-maxfail=2` or greater will turn off any handling of maxfail within this plugin and the behavior is controlled by pytest.

In other words, the `maxfail` count is counting tests, not checks.
The exception is the case of `1`, where we want to stop on the very first failed check.

## any_failures()

Use `any_failures()` to see if there are any failures.  
One use case is to make a block of checks conditional on not failing in a previous set of checks:

```python
from pytest_check import check

def test_with_groups_of_checks():
    # always check these
    check.equal(1, 1)
    check.equal(2, 3)
    if not check.any_failures():
        # only check these if the above passed
        check.equal(1, 2)
        check.equal(2, 2)
```

## Speedups

If you have lots of check failures, your tests may not run as fast as you want.
There are a few ways to speed things up.

* `--check-max-tb=5` - Only first 5 failures per test will include pseudo-tracebacks (rest without them).
    * The example shows `5` but any number can be used.
    * pytest-check uses custom traceback code I'm calling a pseudo-traceback.
    * This is visually shorter than normal assert tracebacks.
    * Internally, it uses introspection, which can be slow.
    * Allowing a limited number of pseudo-tracebacks speeds things up quite a bit.
    * Default is 1. 
        * Set a large number, e.g: 1000, if you want pseudo-tracebacks for all failures

* `--check-max-report=10` - limit reported failures per test.
    * The example shows `10` but any number can be used.
    * The test will still have the total nuber of failures reported.
    * Default is no maximum.

* `--check-max-fail=20` - Stop the test after this many check failures.
    * This is useful if your code under test is slow-ish and you want to bail early.
    * Default is no maximum.

* Any of these can be used on their own, or combined.

* Recommendation:
    * Leave the default, equivelant to `--check-max-tb=1`.
    * If excessive output is annoying, set `--check-max-report=10` or some tolerable number.

## Local speedups

The flags above are global settings, and apply to every test in the test run.  

Locally, you can set these values per test.

From `examples/test_example_speedup_funcs.py`:

```python
def test_max_tb():
    check.set_max_tb(2)
    for i in range(1, 11):
        check.equal(i, 100)

def test_max_report():
    check.set_max_report(5)
    for i in range(1, 11):
        check.equal(i, 100)

def test_max_fail():
    check.set_max_fail(5)
    for i in range(1, 11):
        check.equal(i, 100)
```

## Call on fail

If you want to have a custom action happen for every check failure,
you can use the method `call_on_fail(func)`.  
You have to pass it a function that accepts a string.  
That function will be called with the message from the check failure. 

Example:

```python
from pytest_check import check

def my_func(msg):
    ...

check.call_on_fail(my_func)
...

```

There are other uses for this, but the original use case idea was for logging to a file.

### Logging to a file

The `examples/logging_to_a_file/` directory has an example of how you could set this up. 

In a `conftest.py` file, we:

* Configure a logging logger to write to a file.
* Create a small `log_failure(message)` function that uses that logger
* Call `check.call_on_fail(log_failure)` to register the function.

And that's it, all failures will get logged to a file.

```python
import logging
import pytest
from pytest_check import check

@pytest.fixture(scope='session', autouse=True)
def setup_logging():
    # logging config
    log = logging.getLogger(__name__)
    log.setLevel(logging.DEBUG)
    fh = logging.FileHandler('session.log')
    fh.setLevel(logging.DEBUG)
    fh.setFormatter(logging.Formatter('--- %(asctime)s.%(msecs)03d ---\n%(message)s', 
                                      datefmt='%Y-%m-%d %H:%M:%S'))
    log.addHandler(fh)
    # log start of tests
    log.info("---------\nStarting test run\n---------")
    # have check failures log to file
    def log_failure(message):
        log.error(message)
    check.call_on_fail(log_failure)
```

With that setup, the file will end up looking something like this:

```
$ cat session.log              
--- 2026-02-26 09:46:39.822 ---
---------
Starting test run
---------
--- 2026-02-26 09:46:39.831 ---
FAILURE: check 1 == 2
test_log2.py:4 in test_one() -> check.equal(1, 2)

--- 2026-02-26 09:46:39.832 ---
FAILURE: check 5 == 6
test_log2.py:7 in test_two() -> check.equal(5, 6)
```

Of course, you can modify the logging config to make it look however you want.


## Contributing

Contributions are very welcome. Tests can be run with [tox](https://tox.readthedocs.io/en/latest/).
Test coverage is now 100%. Please make sure to keep it at 100%.
If you have an awesome pull request and need help with getting coverage back up, let me know.


## License

Distributed under the terms of the [MIT](http://opensource.org/licenses/MIT) license, "pytest-check" is free and open source software

## Issues

If you encounter any problems, please [file an issue](https://github.com/okken/pytest-check/issues) along with a detailed description.

## Changelog

See [changelog.md](https://github.com/okken/pytest-check/blob/main/changelog.md)

