Decorator Matchers¶
Matchers that decorate other matchers for better expression.
described_as¶
-
class
hamcrest.core.core.described_as.DescribedAs(description_template, matcher, *values)¶ Bases:
hamcrest.core.base_matcher.BaseMatcher-
describe_mismatch(item, mismatch_description)¶ Generates a description of why the matcher has not accepted the item.
The description will be part of a larger description of why a matching failed, so it should be concise.
This method assumes that
matches(item)isFalse, but will not check this.- Parameters
item – The item that the
Matcherhas rejected.mismatch_description – The description to be built or appended to.
-
describe_to(description)¶ Generates a description of the object.
The description may be part of a description of a larger object of which this is just a component, so it should be worded appropriately.
- Parameters
description – The description to be built or appended to.
-
matches(item, mismatch_description=None)¶ Evaluates the matcher for argument item.
If a mismatch is detected and argument
mismatch_descriptionis provided, it will generate a description of why the matcher has not accepted the item.- Parameters
item – The object against which the matcher is evaluated.
- Returns
Trueifitemmatches, otherwiseFalse.
-
-
hamcrest.core.core.described_as.described_as(description, matcher[, value1[, ...]])¶ Adds custom failure description to a given matcher.
- Parameters
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.
is_¶
-
class
hamcrest.core.core.is_.Is(matcher)¶ Bases:
hamcrest.core.base_matcher.BaseMatcher-
describe_mismatch(item, mismatch_description)¶ Generates a description of why the matcher has not accepted the item.
The description will be part of a larger description of why a matching failed, so it should be concise.
This method assumes that
matches(item)isFalse, but will not check this.- Parameters
item – The item that the
Matcherhas rejected.mismatch_description – The description to be built or appended to.
-
describe_to(description)¶ Generates a description of the object.
The description may be part of a description of a larger object of which this is just a component, so it should be worded appropriately.
- Parameters
description – The description to be built or appended to.
-
matches(item, mismatch_description=None)¶ Evaluates the matcher for argument item.
If a mismatch is detected and argument
mismatch_descriptionis provided, it will generate a description of why the matcher has not accepted the item.- Parameters
item – The object against which the matcher is evaluated.
- Returns
Trueifitemmatches, otherwiseFalse.
-
-
hamcrest.core.core.is_.is_(x)¶ Decorates another matcher, or provides shortcuts to the frequently used
is(equal_to(x))andis(instance_of(x)).- Parameters
x – The matcher to satisfy, or a type for
instance_ofmatching, or an expected value forequal_tomatching.
This matcher compares the evaluated object to the given matcher.
Note
PyHamcrest’s
is_matcher is unrelated to Python’sisoperator. The matcher for object identity issame_instance.If the
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)))
If the
xargument is a type, it is wrapped in aninstance_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 anequal_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.