Matchers that decorate other matchers for better expression.
described_as(description, matcher[, value1[, ...]])¶
Adds custom failure description to a given matcher.
- description – Overrides the matcher’s description.
- matcher – The matcher to satisfy.
- value1,... – Optional comma-separated list of substitution values.
The description may contain substitution placeholders %0, %1, etc. These will be replaced by any values that follow the matcher.
Decorates another matcher, or provides shortcuts to the frequently used
Parameters: x – The matcher to satisfy, or a type for
instance_ofmatching, or an expected value for
This matcher compares the evaluated object to the given matcher.
is_matcher is unrelated to Python’s
isoperator. The matcher for object identity is
xargument is a matcher, its behavior is retained, but the test may be more expressive. For example:
assert_that(value, less_than(5)) assert_that(value, is_(less_than(5)))
xargument is a type, it is wrapped in an
instance_ofmatcher. This makes the following statements equivalent:
assert_that(cheese, instance_of(Cheddar)) assert_that(cheese, is_(instance_of(Cheddar))) assert_that(cheese, is_(Cheddar))
Otherwise, if the
xargument is not a matcher, it is wrapped in an
equal_tomatcher. This makes the following statements equivalent:
assert_that(cheese, equal_to(smelly)) assert_that(cheese, is_(equal_to(smelly))) assert_that(cheese, is_(smelly))
Choose the style that makes your expression most readable. This will vary depending on context.