rspec/rules/S5905/python/rule.adoc

This rule raises an issue when using an ``++assert++`` statement on a tuple literal.

== Why is this an issue?

When tested for truthiness, a sequence or collection will evaluate to `False` if it is empty (its ``++__len__++`` method returns 0) and to `True` if it contains at least one element.

Using the ``assert`` statement on a tuple literal will therefore always fail if the tuple is empty, and always succeed otherwise.

The ``++assert++`` statement does not take parentheses around its parameters. Calling ``++assert(x, y)++`` will test if the tuple ``++(x, y)++`` is True, which is always the case.


There are two possible fixes:

* If your intention is to test the first value of the tuple and use the second value as a message, simply remove the parentheses.
* If your intention is to check that every element of the tuple is ``++True++``, test each value separately.

=== Code examples

==== Noncompliant code example

[source,python]
----
def test_values(a, b):
    assert (a, b)  # Noncompliant: will always be True
----


==== Compliant solution

[source,python]
----
def test_values(a, b):
    # If you mean to test "a" and use "b" as an error message
    assert a, b

    # If you mean to test the values of "a" and "b"
    assert a and b
----


== Resources

* https://docs.python.org/3/reference/simple_stmts.html#the-assert-statement[Python documentation - The ``++assert++`` statement]
* https://docs.python.org/3/library/stdtypes.html#truth-value-testing[Python documentation - Truth Value Testing]

ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

Fix this assertion on a tuple literal; did you mean "assert A, B".


=== Highlighting

The tuple parameter


'''
== Comments And Links
(visible only on this page)

=== deprecates: S1721

endif::env-github,rspecator-view[]