Source code for _pytest.assertion

support for presenting detailed information in failing assertions.
import sys

from _pytest.assertion import rewrite
from _pytest.assertion import truncate
from _pytest.assertion import util

def pytest_addoption(parser):
    group = parser.getgroup("debugconfig")
        choices=("rewrite", "plain"),
        help="""Control assertion debugging tools.  'plain'
                            performs no assertion debugging.  'rewrite'
                            (the default) rewrites assert statements in
                            test modules on import to provide assert
                            expression information.""",
        help="Enables the pytest_assertion_pass hook."
        "Make sure to delete any previously generated pyc cache files.",

[docs]def register_assert_rewrite(*names): """Register one or more module names to be rewritten on import. This function will make sure that this module or all modules inside the package will get their assert statements rewritten. Thus you should make sure to call this before the module is actually imported, usually in your if you are a plugin using a package. :raise TypeError: if the given module names are not strings. """ for name in names: if not isinstance(name, str): msg = "expected module names as *args, got {0} instead" raise TypeError(msg.format(repr(names))) for hook in sys.meta_path: if isinstance(hook, rewrite.AssertionRewritingHook): importhook = hook break else: importhook = DummyRewriteHook() importhook.mark_rewrite(*names)
class DummyRewriteHook: """A no-op import hook for when rewriting is disabled.""" def mark_rewrite(self, *names): pass class AssertionState: """State for the assertion plugin.""" def __init__(self, config, mode): self.mode = mode self.trace = config.trace.root.get("assertion") self.hook = None def install_importhook(config): """Try to install the rewrite hook, raise SystemError if it fails.""" config._assertstate = AssertionState(config, "rewrite") config._assertstate.hook = hook = rewrite.AssertionRewritingHook(config) sys.meta_path.insert(0, hook) config._assertstate.trace("installed rewrite import hook") def undo(): hook = config._assertstate.hook if hook is not None and hook in sys.meta_path: sys.meta_path.remove(hook) config.add_cleanup(undo) return hook def pytest_collection(session): # this hook is only called when test modules are collected # so for example not in the master process of pytest-xdist # (which does not collect test modules) assertstate = getattr(session.config, "_assertstate", None) if assertstate: if assertstate.hook is not None: assertstate.hook.set_session(session) def pytest_runtest_setup(item): """Setup the pytest_assertrepr_compare and pytest_assertion_pass hooks The newinterpret and rewrite modules will use util._reprcompare if it exists to use custom reporting via the pytest_assertrepr_compare hook. This sets up this custom comparison for the test. """ def callbinrepr(op, left, right): """Call the pytest_assertrepr_compare hook and prepare the result This uses the first result from the hook and then ensures the following: * Overly verbose explanations are truncated unless configured otherwise (eg. if running in verbose mode). * Embedded newlines are escaped to help util.format_explanation() later. * If the rewrite mode is used embedded %-characters are replaced to protect later % formatting. The result can be formatted by util.format_explanation() for pretty printing. """ hook_result = item.ihook.pytest_assertrepr_compare( config=item.config, op=op, left=left, right=right ) for new_expl in hook_result: if new_expl: new_expl = truncate.truncate_if_required(new_expl, item) new_expl = [line.replace("\n", "\\n") for line in new_expl] res = "\n~".join(new_expl) if item.config.getvalue("assertmode") == "rewrite": res = res.replace("%", "%%") return res util._reprcompare = callbinrepr if item.ihook.pytest_assertion_pass.get_hookimpls(): def call_assertion_pass_hook(lineno, expl, orig): item.ihook.pytest_assertion_pass( item=item, lineno=lineno, orig=orig, expl=expl ) util._assertion_pass = call_assertion_pass_hook def pytest_runtest_teardown(item): util._reprcompare = None util._assertion_pass = None def pytest_sessionfinish(session): assertstate = getattr(session.config, "_assertstate", None) if assertstate: if assertstate.hook is not None: assertstate.hook.set_session(None) # Expose this plugin's implementation for the pytest_assertrepr_compare hook pytest_assertrepr_compare = util.assertrepr_compare