FAILURE_EXCEPTION = AssertionError


def fail(msg=None):
    """Fail immediately, with the given message."""
    raise FAILURE_EXCEPTION, msg

def assert_false(expr, msg=None):
    "Fail the test if the expression is true."
    if expr: raise FAILURE_EXCEPTION, msg

def assert_true(expr, msg=None):
    """Fail the test unless the expression is true."""
    if not expr: raise FAILURE_EXCEPTION, msg

def assert_raises(excClass, callableObj, *args, **kwargs):
    """Fail unless an exception of class excClass is thrown
       by callableObj when invoked with arguments args and keyword
       arguments kwargs. If a different type of exception is
       thrown, it will not be caught, and the test case will be
       deemed to have suffered an error, exactly as for an
       unexpected exception.
    """
    try:
        callableObj(*args, **kwargs)
    except excClass:
        return
    else:
        if hasattr(excClass,'__name__'): excName = excClass.__name__
        else: excName = str(excClass)
        raise FAILURE_EXCEPTION, "%s not raised" % excName

def assert_equal(first, second, msg=None):
    """Fail if the two objects are unequal as determined by the '=='
       operator.
    """
    if not first == second:
        raise FAILURE_EXCEPTION, (msg or '%r != %r' % (first, second))

def asssert_not_equal(first, second, msg=None):
    """Fail if the two objects are equal as determined by the '=='
       operator.
    """
    if first == second:
        raise FAILURE_EXCEPTION, (msg or '%r == %r' % (first, second))

def assert_almost_equal(first, second, places=7, msg=None):
    """Fail if the two objects are unequal as determined by their
       difference rounded to the given number of decimal places
       (default 7) and comparing to zero.
    
       Note that decimal places (from zero) are usually not the same
       as significant digits (measured from the most signficant digit).
    """
    if round(second-first, places) != 0:
        raise FAILURE_EXCEPTION, \
              (msg or '%r != %r within %r places' % (first, second, places))

def assert_not_almost_equal(first, second, places=7, msg=None):
    """Fail if the two objects are equal as determined by their
       difference rounded to the given number of decimal places
       (default 7) and comparing to zero.
    
       Note that decimal places (from zero) are usually not the same
       as significant digits (measured from the most signficant digit).
    """
    if round(second-first, places) == 0:
        raise FAILURE_EXCEPTION, \
              (msg or '%r == %r within %r places' % (first, second, places))