plugin.py

import pytest
import inspect
import os.path

@pytest.fixture
def expect(request):
    def do_expect(expr, msg=''):
        if not expr:
            _log_failure(request.node, msg)
    return do_expect

def _log_failure(node, msg=''):
    # get filename, line, and context
    (filename, line, funcname, contextlist) =  inspect.stack()[2][1:5]
    filename = os.path.basename(filename)
    context = contextlist[0]
    # format entry
    msg = '%s\n' % msg if msg else ''
    entry = '>%s%s%s:%s\n--------' % (context, msg, filename, line)
    # add entry 
    if not hasattr(node, '_failed_expect'):
        node._failed_expect = []
    node._failed_expect.append(entry)

@pytest.mark.hookwrapper
def pytest_runtest_makereport(item, call):
    outcome = yield
    report = outcome.get_result()
    if (call.when == "call") and hasattr(item, '_failed_expect'):
        summary = 'Failed Expectations:%s' % len(item._failed_expect)
        item._failed_expect.append(summary)
        if report.longrepr:
            report.longrepr = str(report.longrepr) + '\n--------\n' + ('\n'.join(item._failed_expect))
        else:
            report.longrepr = '\n'.join(item._failed_expect)
        report.outcome = "failed"