OCHamcrest is an Objective-C module providing:
- a library of "matcher" objects for declaring rules to check whether a given object matches those rules.
- a framework for writing your own matchers.
Matchers can be combined to create flexible expressions of intent in tests. They can also be used for other purposes, such as user input validation.
- My First OCHamcrest Test
- Predefined Matchers
- Common Questions
- How Do I Add OCHamcrest to My Project?
- Author
We'll start by writing a very simple Xcode unit test, but instead of using XCTest's
XCTAssertEqualObjects
function, we'll use OCHamcrest's assertThat
construct and a predefined
matcher:
@import OCHamcrest;
@import XCTest;
@interface BiscuitTest : XCTestCase
@end
@implementation BiscuitTest
- (void)testEquals
{
Biscuit* theBiscuit = [[Biscuit alloc] initWithName:@"Ginger"];
Biscuit* myBiscuit = [[Biscuit alloc] initWithName:@"Ginger"];
assertThat(theBiscuit, equalTo(myBiscuit));
}
@end
The assertThat
function is a stylized sentence for making a test assertion. In this example, the
subject of the assertion is the object theBiscuit
, which is the first method parameter. The second
method parameter is a matcher for Biscuit
objects, here a matcher that checks one object is equal
to another using the -isEqual:
method. The test passes since the Biscuit
class defines an
-isEqual:
method.
OCHamcrest's functions are actually declared with an "HC_" package prefix (such as HC_assertThat
and HC_equalTo
) to avoid name clashes. To make test writing faster and test code more legible,
optional short syntax is provided by default. For example, instead of writing HC_assertThat
,
simply write assertThat
.
OCHamcrest comes with a library of useful matchers:
conformsTo
- match object that conforms to protocolequalTo
- match equal objecthasDescription
- match object's-description
hasProperty
- match return value of method with given nameinstanceOf
- match object typeisA
- match object type precisely, no subclassesnilValue
,notNilValue
- matchnil
, or notnil
sameInstance
- match same objectthrowsException
- match block that throws an exception- HCArgumentCaptor - match anything, capturing all values
closeTo
- match number close to a given valuegreaterThan
,greaterThanOrEqualTo
,lessThan
,lessThanOrEqualTo
- match numeric orderingisFalse
- match zeroisTrue
- match non-zero
containsSubstring
- match part of a stringendsWith
- match the end of a stringequalToIgnoringCase
- match the complete string but ignore caseequalToIgnoringWhitespace
- match the complete string but ignore extra whitespacestartsWith
- match the beginning of a stringstringContainsInOrder
,stringContainsInOrderIn
- match parts of a string, in relative order
allOf
,allOfIn
- "and" together all matchersanyOf
,anyOfIn
- "or" together all matchersanything
- match anything (useful in composite matchers when you don't care about a particular value)isNot
- negate the matcher
contains
,containsIn
- exactly match the entire collectioncontainsInAnyOrder
,containsInAnyOrderIn
- match the entire collection, but in any ordercontainsInRelativeOrder
,containsInRelativeOrderIn
- match collection containing items in relative ordereveryItem
- match if every item in a collection satisfies a given matcherhasCount
- match number of elements against another matcherhasCountOf
- match collection with given number of elementshasEntries
- match dictionary with key-value pairs in a dictionaryhasEntriesIn
- match dictionary with key-value pairs in a listhasEntry
- match dictionary containing a key-value pairhasItem
- match if given item appears in the collectionhasItems
,hasItemsIn
- match if all given items appear in the collection, in any orderhasKey
- match dictionary with a keyhasValue
- match dictionary with a valueisEmpty
- match empty collectionisIn
- match when object is in given collectiononlyContains
,onlyContainsIn
- match if collection's items appear in given list
describedAs
- give the matcher a custom failure descriptionis
- decorator to improve readability - see "Syntactic sugar" below
The arguments for many of these matchers accept not just a matching value, but
another matcher, so matchers can be composed for greater flexibility. For
example, only_contains(endsWith(@"."))
will match any collection where every
item is a string ending with period.
OCHamcrest strives to make your tests as readable as possible. For example, the is
matcher is a
wrapper that doesn't add any extra behavior to the underlying matcher. The following assertions are
all equivalent:
assertThat(theBiscuit, equalTo(myBiscuit));
assertThat(theBiscuit, is(equalTo(myBiscuit)));
assertThat(theBiscuit, is(myBiscuit));
The last form is allowed since is
wraps non-matcher arguments with equalTo
. Other matchers that
take matchers as arguments provide similar shortcuts, wrapping non-matcher arguments in equalTo
.
assertWithTimeout
will keep evaluating an expression until the matcher is satisfied or a timeout
is reached. For example,
assertWithTimeout(5, thatEventually(self.someString), is(@"expected"));
This repeatedly checks for this string to evaluate to "expected" before timing out after 5 seconds.
thatEventually
is a convenience macro to create a block.
OCHamcrest comes bundled with lots of useful matchers, but you'll probably find that you need to create your own from time to time to fit your testing needs. See the "Writing Custom Matchers" guide for more information.
Try the native Swift implementation of Hamcrest.
The Examples folder shows projects ready to use OCHamcrest via Swift Package Manager, CocoaPods, or through the prebuilt framework.
Include an OCHamcrest package in your Package.swift manifest's array of dependencies
:
dependencies: [
.package(
url: "https://github.com/hamcrest/OCHamcrest",
.upToNextMajor(from: "9.0.0")
),
],
Then add OCHamcrest to the dependencies of your .testTarget
:
.testTarget(
name: "ExampleTests",
dependencies: [
"Example",
"OCHamcrest",
]
),
If you want to add OCHamcrest using Cocoapods then add the following dependency to your Podfile. Most people will want OCHamcrest in their test targets, and not include any pods from their main targets:
target 'MyTests' do
inherit! :search_paths
use_frameworks!
pod 'OCHamcrest', '~> 9.0'
end
Add the following to your Cartfile:
github "hamcrest/OCHamcrest" ~> 9.0
Then drag the the built framework from the appropriate Carthage/Build directory into your project, but with "Copy items into destination group's folder" disabled.
A prebuilt binary is available on GitHub. The binary is packaged as OCHamcrest.xcframework, containing these architectures:
- macOS
- Mac Catalyst
- iOS device
- iOS simulator
- tvOS device
- tvOS simulator
- watchOS device
- watchOS simulator
Drag the XCFramework into your project.
If you want to build OCHamcrest yourself, clone the repo, then
$ cd Source
$ ./MakeDistribution.sh
Jon Reid is the author of iOS Unit Testing by Example. His website is Quality Coding.