Object Matchers

Matchers that inspect objects.

equal_to

class hamcrest.core.core.isequal.IsEqual(equals)

Bases: hamcrest.core.base_matcher.BaseMatcher

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.
hamcrest.core.core.isequal.equal_to(obj)

Matches if object is equal to a given object.

Parameters:obj – The object to compare against as the expected value.

This matcher compares the evaluated object to obj for equality.

has_length

class hamcrest.library.object.haslength.HasLength(len_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) is False, but will not check this.

Parameters:
  • item – The item that the Matcher has 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.
hamcrest.library.object.haslength.has_length(match)

Matches if len(item) satisfies a given matcher.

Parameters:match – The matcher to satisfy, or an expected value for equal_to matching.

This matcher invokes the len function on the evaluated object to get its length, passing the result to a given matcher for evaluation.

If the match argument is not a matcher, it is implicitly wrapped in an equal_to matcher to check for :equality.

Examples:

has_length(greater_than(6))
has_length(5)

has_string

class hamcrest.library.object.hasstring.HasString(str_matcher)

Bases: hamcrest.core.base_matcher.BaseMatcher

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.
hamcrest.library.object.hasstring.has_string(match)

Matches if str(item) satisfies a given matcher.

Parameters:match – The matcher to satisfy, or an expected value for equal_to matching.

This matcher invokes the str function on the evaluated object to get its length, passing the result to a given matcher for evaluation. If the match argument is not a matcher, it is implicitly wrapped in an equal_to matcher to check for equality.

Examples:

has_string(starts_with('foo'))
has_string('bar')

has_properties/has_property

class hamcrest.library.object.hasproperty.IsObjectWithProperty(property_name, value_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) is False, but will not check this.

Parameters:
  • item – The item that the Matcher has 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.
hamcrest.library.object.hasproperty.has_properties(*keys_valuematchers, **kv_args)

Matches if an object has properties satisfying all of a dictionary of string property names and corresponding value matchers.

Parameters:matcher_dict – A dictionary mapping keys to associated value matchers, or to expected values for equal_to matching.

Note that the keys must be actual keys, not matchers. Any value argument that is not a matcher is implicitly wrapped in an equal_to matcher to check for equality.

Examples:

has_properties({'foo':equal_to(1), 'bar':equal_to(2)})
has_properties({'foo':1, 'bar':2})

has_properties also accepts a list of keyword arguments:

hamcrest.library.object.hasproperty.has_properties(keyword1=value_matcher1[, keyword2=value_matcher2[, ...]])
Parameters:
  • keyword1 – A keyword to look up.
  • valueMatcher1 – The matcher to satisfy for the value, or an expected value for equal_to matching.

Examples:

has_properties(foo=equal_to(1), bar=equal_to(2))
has_properties(foo=1, bar=2)

Finally, has_properties also accepts a list of alternating keys and their value matchers:

hamcrest.library.object.hasproperty.has_properties(key1, value_matcher1[, ...])
Parameters:
  • key1 – A key (not a matcher) to look up.
  • valueMatcher1 – The matcher to satisfy for the value, or an expected value for equal_to matching.

Examples:

has_properties('foo', equal_to(1), 'bar', equal_to(2))
has_properties('foo', 1, 'bar', 2)
hamcrest.library.object.hasproperty.has_property(name, match=None)

Matches if object has a property with a given name whose value satisfies a given matcher.

Parameters:
  • name – The name of the property.
  • match – Optional matcher to satisfy.

This matcher determines if the evaluated object has a property with a given name. If no such property is found, has_property is not satisfied.

If the property is found, its value is passed to a given matcher for evaluation. If the match argument is not a matcher, it is implicitly wrapped in an equal_to matcher to check for equality.

If the match argument is not provided, the anything matcher is used so that has_property is satisfied if a matching property is found.

Examples:

has_property('name', starts_with('J'))
has_property('name', 'Jon')
has_property('name')

instance_of

class hamcrest.core.core.isinstanceof.IsInstanceOf(expected_type)

Bases: hamcrest.core.base_matcher.BaseMatcher

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.
hamcrest.core.core.isinstanceof.instance_of(atype)

Matches if object is an instance of, or inherits from, a given type.

Parameters:atype – The type to compare against as the expected type or a tuple of types.

This matcher checks whether the evaluated object is an instance of atype or an instance of any class that inherits from atype.

Example:

instance_of(str)

none, not_none

class hamcrest.core.core.isnone.IsNone

Bases: hamcrest.core.base_matcher.BaseMatcher

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.
hamcrest.core.core.isnone.none()

Matches if object is None.

hamcrest.core.core.isnone.not_none()

Matches if object is not None.

same_instance

class hamcrest.core.core.issame.IsSame(object)

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) is False, but will not check this.

Parameters:
  • item – The item that the Matcher has 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.
hamcrest.core.core.issame.same_instance(obj)

Matches if evaluated object is the same instance as a given object.

Parameters:obj – The object to compare against as the expected value.

This matcher invokes the is identity operator to determine if the evaluated object is the the same object as obj.

calling, raises

class hamcrest.core.core.raises.Raises(expected, pattern=None)

Bases: hamcrest.core.base_matcher.BaseMatcher

describe_mismatch(item, 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) is False, but will not check this.

Parameters:
  • item – The item that the Matcher has 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.
hamcrest.core.core.raises.calling(func)

Wrapper for function call that delays the actual execution so that raises matcher can catch any thrown exception.

Parameters:func – The function or method to be called

The arguments can be provided with a call to the with_args function on the returned object:

calling(my_method).with_args(arguments, and_='keywords')
hamcrest.core.core.raises.raises(exception, pattern=None)

Matches if the called function raised the expected exception.

Parameters:
  • exception – The class of the expected exception
  • pattern – Optional regular expression to match exception message.

Expects the actual to be wrapped by using calling, or a callable taking no arguments. Optional argument pattern should be a string containing a regular expression. If provided, the string representation of the actual exception - e.g. str(actual) - must match pattern.

Examples:

assert_that(calling(int).with_args('q'), raises(TypeError))
assert_that(calling(parse, broken_input), raises(ValueError))