Nimble

Use Nimble to express the expected outcomes of Swift or Objective-C expressions. Inspired by Cedar.

// Swift

expect(1 + 1).to(equal(2))
expect(1.2).to(beCloseTo(1.1, within: 0.1))
expect(3) > 2
expect("seahorse").to(contain("sea"))
expect(["Atlantic", "Pacific"]).toNot(contain("Mississippi"))
expect(ocean.isClean).toEventually(beTruthy())

How to Use Nimble

Table of Contents generated with DocToc

Some Background: Expressing Outcomes Using Assertions in XCTest
Nimble: Expectations Using expect(...).to
Built-in Matcher Functions
Writing Your Own Matchers
- Lazy Evaluation
- Type Checking via Swift Generics
- Customizing Failure Messages
- Supporting Objective-C
  - Properly Handling nil in Objective-C Matchers
Installing Nimble

Some Background: Expressing Outcomes Using Assertions in XCTest

Apple's Xcode includes the XCTest framework, which provides assertion macros to test whether code behaves properly. For example, to assert that 1 + 1 = 2, XCTest has you write:

// Swift

XCTAssertEqual(1 + 1, 2, "expected one plus one to equal two")

Or, in Objective-C:

// Objective-C

XCTAssertEqual(1 + 1, 2, @"expected one plus one to equal two");

XCTest assertions have a couple of drawbacks:

Not enough macros. There's no easy way to assert that a string contains a particular substring, or that a number is less than or equal to another.
It's hard to write asynchronous tests. XCTest forces you to write a lot of boilerplate code.

Nimble addresses these concerns.

Nimble: Expectations Using `expect(...).to`

Nimble allows you to express expectations using a natural, easily understood language:

// Swift

import Nimble

expect(seagull.squawk).to(equal("Squee!"))

// Objective-C

@import Nimble;

expect(seagull.squawk).to(equal(@"Squee!"));

The expect function autocompletes to include file: and line:, but these parameters are optional. Use the default values to have Xcode highlight the correct line when an expectation is not met.

To perform the opposite expectation--to assert something is not equal--use toNot or notTo:

// Swift

import Nimble

expect(seagull.squawk).toNot(equal("Oh, hello there!"))
expect(seagull.squawk).notTo(equal("Oh, hello there!"))

// Objective-C

@import Nimble;

expect(seagull.squawk).toNot(equal(@"Oh, hello there!"));
expect(seagull.squawk).notTo(equal(@"Oh, hello there!"));

Custom Failure Messages

Would you like to add more information to the test's failure messages? Use the description optional argument to add your own text:

// Swift

expect(1 + 1).to(equal(3))
// failed - expected to equal <3>, got <2>

expect(1 + 1).to(equal(3), description: "Make sure libKindergartenMath is loaded")
// failed - Make sure libKindergartenMath is loaded
// expected to equal <3>, got <2>

Or the *WithDescription version in Objective-C:

// Objective-C

@import Nimble;

expect(@(1+1)).to(equal(@3));
// failed - expected to equal <3.0000>, got <2.0000>

expect(@(1+1)).toWithDescription(equal(@3), @"Make sure libKindergartenMath is loaded");
// failed - Make sure libKindergartenMath is loaded
// expected to equal <3.0000>, got <2.0000>

Type Checking

Nimble makes sure you don't compare two types that don't match:

// Swift

// Does not compile:
expect(1 + 1).to(equal("Squee!"))

Nimble uses generics--only available in Swift--to ensure type correctness. That means type checking is not available when using Nimble in Objective-C. 😭

Operator Overloads

Tired of so much typing? With Nimble, you can use overloaded operators like == for equivalence, or > for comparisons:

// Swift

// Passes if squawk does not equal "Hi!":
expect(seagull.squawk) != "Hi!"

// Passes if 10 is greater than 2:
expect(10) > 2

Operator overloads are only available in Swift, so you won't be able to use this syntax in Objective-C. 💔

Lazily Computed Values

The expect function doesn't evaluate the value it's given until it's time to match. So Nimble can test whether an expression raises an exception once evaluated:

// Swift

// Note: Swift currently doesn't have exceptions.
//       Only Objective-C code can raise exceptions
//       that Nimble will catch.
//       (see https://github.com/Quick/Nimble/issues/220#issuecomment-172667064)
let exception = NSException(
  name: NSInternalInconsistencyException,
  reason: "Not enough fish in the sea.",
  userInfo: ["something": "is fishy"])
expect { exception.raise() }.to(raiseException())

// Also, you can customize raiseException to be more specific
expect { exception.raise() }.to(raiseException(named: NSInternalInconsistencyException))
expect { exception.raise() }.to(raiseException(
    named: NSInternalInconsistencyException,
    reason: "Not enough fish in the sea"))
expect { exception.raise() }.to(raiseException(
    named: NSInternalInconsistencyException,
    reason: "Not enough fish in the sea",
    userInfo: ["something": "is fishy"]))

Objective-C works the same way, but you must use the expectAction macro when making an expectation on an expression that has no return value:

// Objective-C

NSException *exception = [NSException exceptionWithName:NSInternalInconsistencyException
                                                 reason:@"Not enough fish in the sea."
                                               userInfo:nil];
expectAction(^{ [exception raise]; }).to(raiseException());

// Use the property-block syntax to be more specific.
expectAction(^{ [exception raise]; }).to(raiseException().named(NSInternalInconsistencyException));
expectAction(^{ [exception raise]; }).to(raiseException().
    named(NSInternalInconsistencyException).
    reason("Not enough fish in the sea"));
expectAction(^{ [exception raise]; }).to(raiseException().
    named(NSInternalInconsistencyException).
    reason("Not enough fish in the sea").
    userInfo(@{@"something": @"is fishy"}));

// You can also pass a block for custom matching of the raised exception
expectAction(exception.raise()).to(raiseException().satisfyingBlock(^(NSException *exception) {
    expect(exception.name).to(beginWith(NSInternalInconsistencyException));
}));

C Primitives

Some testing frameworks make it hard to test primitive C values. In Nimble, it just works:

// Swift

let actual: CInt = 1
let expectedValue: CInt = 1
expect(actual).to(equal(expectedValue))

In fact, Nimble uses type inference, so you can write the above without explicitly specifying both types:

// Swift

expect(1 as CInt).to(equal(1))

In Objective-C, Nimble only supports Objective-C objects. To make expectations on primitive C values, wrap then in an object literal:

expect(@(1 + 1)).to(equal(@2));

Asynchronous Expectations

In Nimble, it's easy to make expectations on values that are updated asynchronously. Just use toEventually or toEventuallyNot:

// Swift

dispatch_async(dispatch_get_main_queue()) {
  ocean.add("dolphins")
  ocean.add("whales")
}
expect(ocean).toEventually(contain("dolphins", "whales"))

// Objective-C
dispatch_async(dispatch_get_main_queue(), ^{
  [ocean add:@"dolphins"];
  [ocean add:@"whales"];
});
expect(ocean).toEventually(contain(@"dolphins", @"whales"));

Note: toEventually triggers its polls on the main thread. Blocking the main thread will cause Nimble to stop the run loop. This can cause test pollution for whatever incomplete code that was running on the main thread. Blocking the main thread can be caused by blocking IO, calls to sleep(), deadlocks, and synchronous IPC.

In the above example, ocean is constantly re-evaluated. If it ever contains dolphins and whales, the expectation passes. If ocean still doesn't contain them, even after being continuously re-evaluated for one whole second, the expectation fails.

Sometimes it takes more than a second for a value to update. In those cases, use the timeout parameter:

// Swift

// Waits three seconds for ocean to contain "starfish":
expect(ocean).toEventually(contain("starfish"), timeout: 3)

// Objective-C

// Waits three seconds for ocean to contain "starfish":
expect(ocean).withTimeout(3).toEventually(contain(@"starfish"));

You can also provide a callback by using the waitUntil function:

// Swift

waitUntil { done in
  // do some stuff that takes a while...
  NSThread.sleepForTimeInterval(0.5)
  done()
}

// Objective-C

waitUntil(^(void (^done)(void)){
  // do some stuff that takes a while...
  [NSThread sleepForTimeInterval:0.5];
  done();
});

waitUntil also optionally takes a timeout parameter:

// Swift

waitUntil(timeout: 10) { done in
  // do some stuff that takes a while...
  NSThread.sleepForTimeInterval(1)
  done()
}

// Objective-C

waitUntilTimeout(10, ^(void (^done)(void)){
  // do some stuff that takes a while...
  [NSThread sleepForTimeInterval:1];
  done();
});

Note: waitUntil triggers its timeout code on the main thread. Blocking the main thread will cause Nimble to stop the run loop to continue. This can cause test pollution for whatever incomplete code that was running on the main thread. Blocking the main thread can be caused by blocking IO, calls to sleep(), deadlocks, and synchronous IPC.

In some cases (e.g. when running on slower machines) it can be useful to modify the default timeout and poll interval values. This can be done as follows:

// Swift

// Increase the global timeout to 5 seconds:
Nimble.Defaults.AsyncTimeout = 5

// Slow the polling interval to 0.1 seconds:
Nimble.Defaults.AsyncPollInterval = 0.1

Objective-C Support

Nimble has full support for Objective-C. However, there are two things to keep in mind when using Nimble in Objective-C:

All parameters passed to the expect function, as well as matcher functions like equal, must be Objective-C objects:

// Objective-C

@import Nimble;

expect(@(1 + 1)).to(equal(@2));
expect(@"Hello world").to(contain(@"world"));

To make an expectation on an expression that does not return a value, such as -[NSException raise], use expectAction instead of expect:
```
// Objective-C

expectAction(^{ [exception raise]; }).to(raiseException());
```

Disabling Objective-C Shorthand

Nimble provides a shorthand for expressing expectations using the expect function. To disable this shorthand in Objective-C, define the NIMBLE_DISABLE_SHORT_SYNTAX macro somewhere in your code before importing Nimble:

#define NIMBLE_DISABLE_SHORT_SYNTAX 1

@import Nimble;

NMB_expect(^{ return seagull.squawk; }, __FILE__, __LINE__).to(NMB_equal(@"Squee!"));

Disabling the shorthand is useful if you're testing functions with names that conflict with Nimble functions, such as expect or equal. If that's not the case, there's no point in disabling the shorthand.

Built-in Matcher Functions

Nimble includes a wide variety of matcher functions.

Equivalence

// Swift

// Passes if actual is equivalent to expected:
expect(actual).to(equal(expected))
expect(actual) == expected

// Passes if actual is not equivalent to expected:
expect(actual).toNot(equal(expected))
expect(actual) != expected

// Objective-C

// Passes if actual is equivalent to expected:
expect(actual).to(equal(expected))

// Passes if actual is not equivalent to expected:
expect(actual).toNot(equal(expected))

Values must be Equatable, Comparable, or subclasses of NSObject. equal will always fail when used to compare one or more nil values.

Identity

// Swift

// Passes if actual has the same pointer address as expected:
expect(actual).to(beIdenticalTo(expected))
expect(actual) === expected

// Passes if actual does not have the same pointer address as expected:
expect(actual).toNot(beIdenticalTo(expected))
expect(actual) !== expected

// Objective-C

// Passes if actual has the same pointer address as expected:
expect(actual).to(beIdenticalTo(expected));

// Passes if actual does not have the same pointer address as expected:
expect(actual).toNot(beIdenticalTo(expected));

Comparisons

// Swift

expect(actual).to(beLessThan(expected))
expect(actual) < expected

expect(actual).to(beLessThanOrEqualTo(expected))
expect(actual) <= expected

expect(actual).to(beGreaterThan(expected))
expect(actual) > expected

expect(actual).to(beGreaterThanOrEqualTo(expected))
expect(actual) >= expected

// Objective-C

expect(actual).to(beLessThan(expected));
expect(actual).to(beLessThanOrEqualTo(expected));
expect(actual).to(beGreaterThan(expected));
expect(actual).to(beGreaterThanOrEqualTo(expected));

Values given to the comparison matchers above must implement Comparable.

Because of how computers represent floating point numbers, assertions that two floating point numbers be equal will sometimes fail. To express that two numbers should be close to one another within a certain margin of error, use beCloseTo:

// Swift

expect(actual).to(beCloseTo(expected, within: delta))

// Objective-C

expect(actual).to(beCloseTo(expected).within(delta));

For example, to assert that 10.01 is close to 10, you can write:

// Swift

expect(10.01).to(beCloseTo(10, within: 0.1))

// Objective-C

expect(@(10.01)).to(beCloseTo(@10).within(0.1));

There is also an operator shortcut available in Swift:

// Swift

expect(actual) ≈ expected
expect(actual) ≈ (expected, delta)

(Type Option-x to get ≈ on a U.S. keyboard)

The former version uses the default delta of 0.0001. Here is yet another way to do this:

// Swift

expect(actual) ≈ expected ± delta
expect(actual) == expected ± delta

(Type Option-Shift-= to get ± on a U.S. keyboard)

If you are comparing arrays of floating point numbers, you'll find the following useful:

// Swift

expect([0.0, 2.0]) ≈ [0.0001, 2.0001]
expect([0.0, 2.0]).to(beCloseTo([0.1, 2.1], within: 0.1))

Values given to the beCloseTo matcher must be coercable into a Double.

Types/Classes

// Swift

// Passes if instance is an instance of aClass:
expect(instance).to(beAnInstanceOf(aClass))

// Passes if instance is an instance of aClass or any of its subclasses:
expect(instance).to(beAKindOf(aClass))

// Objective-C

// Passes if instance is an instance of aClass:
expect(instance).to(beAnInstanceOf(aClass));

// Passes if instance is an instance of aClass or any of its subclasses:
expect(instance).to(beAKindOf(aClass));

Instances must be Objective-C objects: subclasses of NSObject, or Swift objects bridged to Objective-C with the @objc prefix.

For example, to assert that dolphin is a kind of Mammal:

// Swift

expect(dolphin).to(beAKindOf(Mammal))

// Objective-C

expect(dolphin).to(beAKindOf([Mammal class]));

beAnInstanceOf uses the -[NSObject isMemberOfClass:] method to test membership. beAKindOf uses -[NSObject isKindOfClass:].

Truthiness

// Passes if actual is not nil, true, or an object with a boolean value of true:
expect(actual).to(beTruthy())

// Passes if actual is only true (not nil or an object conforming to BooleanType true):
expect(actual).to(beTrue())

// Passes if actual is nil, false, or an object with a boolean value of false:
expect(actual).to(beFalsy())

// Passes if actual is only false (not nil or an object conforming to BooleanType false):
expect(actual).to(beFalse())

// Passes if actual is nil:
expect(actual).to(beNil())

// Objective-C

// Passes if actual is not nil, true, or an object with a boolean value of true:
expect(actual).to(beTruthy());

// Passes if actual is only true (not nil or an object conforming to BooleanType true):
expect(actual).to(beTrue());

// Passes if actual is nil, false, or an object with a boolean value of false:
expect(actual).to(beFalsy());

// Passes if actual is only false (not nil or an object conforming to BooleanType false):
expect(actual).to(beFalse());

// Passes if actual is nil:
expect(actual).to(beNil());

Swift Error Handling

If you're using Swift 2.0+, you can use the throwError matcher to check if an error is thrown.

// Swift

// Passes if somethingThatThrows() throws an ErrorType:
expect{ try somethingThatThrows() }.to(throwError())

// Passes if somethingThatThrows() throws an error with a given domain:
expect{ try somethingThatThrows() }.to(throwError { (error: ErrorType) in
    expect(error._domain).to(equal(NSCocoaErrorDomain))
})

// Passes if somethingThatThrows() throws an error with a given case:
expect{ try somethingThatThrows() }.to(throwError(NSCocoaError.PropertyListReadCorruptError))

// Passes if somethingThatThrows() throws an error with a given type:
expect{ try somethingThatThrows() }.to(throwError(errorType: MyError.self))

If you are working directly with ErrorType values, as is sometimes the case when using Result or Promise types, you can use the matchError matcher to check if the error is the same error is is supposed to be, without requiring explicit casting.

// Swift

let actual: ErrorType = …

// Passes if actual contains any error value from the MyErrorEnum type:
expect(actual).to(matchError(MyErrorEnum))

// Passes if actual contains the Timeout value from the MyErrorEnum type:
expect(actual).to(matchError(MyErrorEnum.Timeout))

// Passes if actual contains an NSError equal to the given one:
expect(actual).to(matchError(NSError(domain: "err", code: 123, userInfo: nil)))

Note: This feature is only available in Swift.

Exceptions

// Swift

// Passes if actual, when evaluated, raises an exception:
expect(actual).to(raiseException())

// Passes if actual raises an exception with the given name:
expect(actual).to(raiseException(named: name))

// Passes if actual raises an exception with the given name and reason:
expect(actual).to(raiseException(named: name, reason: reason))

// Passes if actual raises an exception and it passes expectations in the block
// (in this case, if name begins with 'a r')
expect { exception.raise() }.to(raiseException { (exception: NSException) in
    expect(exception.name).to(beginWith("a r"))
})

// Objective-C

// Passes if actual, when evaluated, raises an exception:
expect(actual).to(raiseException())

// Passes if actual raises an exception with the given name
expect(actual).to(raiseException().named(name))

// Passes if actual raises an exception with the given name and reason:
expect(actual).to(raiseException().named(name).reason(reason))

// Passes if actual raises an exception and it passes expectations in the block
// (in this case, if name begins with 'a r')
expect(actual).to(raiseException().satisfyingBlock(^(NSException *exception) {
    expect(exception.name).to(beginWith(@"a r"));
}));

Note: Swift currently doesn't have exceptions (see #220). Only Objective-C code can raise exceptions that Nimble will catch.

Collection Membership

// Swift

// Passes if all of the expected values are members of actual:
expect(actual).to(contain(expected...))

// Passes if actual is an empty collection (it contains no elements):
expect(actual).to(beEmpty())

// Objective-C

// Passes if expected is a member of actual:
expect(actual).to(contain(expected));

// Passes if actual is an empty collection (it contains no elements):
expect(actual).to(beEmpty());

In Swift contain takes any number of arguments. The expectation passes if all of them are members of the collection. In Objective-C, contain only takes one argument for now.

For example, to assert that a list of sea creature names contains "dolphin" and "starfish":

// Swift

expect(["whale", "dolphin", "starfish"]).to(contain("dolphin", "starfish"))

// Objective-C

expect(@[@"whale", @"dolphin", @"starfish"]).to(contain(@"dolphin"));
expect(@[@"whale", @"dolphin", @"starfish"]).to(contain(@"starfish"));

contain and beEmpty expect collections to be instances of NSArray, NSSet, or a Swift collection composed of Equatable elements.

To test whether a set of elements is present at the beginning or end of an ordered collection, use beginWith and endWith:

// Swift

// Passes if the elements in expected appear at the beginning of actual:
expect(actual).to(beginWith(expected...))

// Passes if the the elements in expected come at the end of actual:
expect(actual).to(endWith(expected...))

// Objective-C

// Passes if the elements in expected appear at the beginning of actual:
expect(actual).to(beginWith(expected));

// Passes if the the elements in expected come at the end of actual:
expect(actual).to(endWith(expected));

beginWith and endWith expect collections to be instances of NSArray, or ordered Swift collections composed of Equatable elements.

Like contain, in Objective-C beginWith and endWith only support a single argument for now.

Strings

// Swift

// Passes if actual contains substring expected:
expect(actual).to(contain(expected))

// Passes if actual begins with substring:
expect(actual).to(beginWith(expected))

// Passes if actual ends with substring:
expect(actual).to(endWith(expected))

// Passes if actual is an empty string, "":
expect(actual).to(beEmpty())

// Passes if actual matches the regular expression defined in expected:
expect(actual).to(match(expected))

// Objective-C

// Passes if actual contains substring expected:
expect(actual).to(contain(expected));

// Passes if actual begins with substring:
expect(actual).to(beginWith(expected));

// Passes if actual ends with substring:
expect(actual).to(endWith(expected));

// Passes if actual is an empty string, "":
expect(actual).to(beEmpty());

// Passes if actual matches the regular expression defined in expected:
expect(actual).to(match(expected))

Checking if all elements of a collection pass a condition

// Swift

// with a custom function:
expect([1,2,3,4]).to(allPass({$0 < 5}))

// with another matcher:
expect([1,2,3,4]).to(allPass(beLessThan(5)))

// Objective-C

expect(@[@1, @2, @3,@4]).to(allPass(beLessThan(@5)));

For Swift the actual value has to be a SequenceType, e.g. an array, a set or a custom seqence type.

For Objective-C the actual value has to be a NSFastEnumeration, e.g. NSArray and NSSet, of NSObjects and only the variant which uses another matcher is available here.

Verify collection count

// passes if actual collection's count is equal to expected
expect(actual).to(haveCount(expected))

// passes if actual collection's count is not equal to expected
expect(actual).notTo(haveCount(expected))

// passes if actual collection's count is equal to expected
expect(actual).to(haveCount(expected))

// passes if actual collection's count is not equal to expected
expect(actual).notTo(haveCount(expected))

For Swift the actual value must be a CollectionType such as array, dictionary or set.

For Objective-C the actual value has to be one of the following classes NSArray, NSDictionary, NSSet, NSHashTable or one of their subclasses.

Matching a value to any of a group of matchers

// passes if actual is either less than 10 or greater than 20
expect(actual).to(satisfyAnyOf(beLessThan(10), beGreaterThan(20)))

// can include any number of matchers -- the following will pass
// **be careful** -- too many matchers can be the sign of an unfocused test
expect(6).to(satisfyAnyOf(equal(2), equal(3), equal(4), equal(5), equal(6), equal(7)))

// in Swift you also have the option to use the || operator to achieve a similar function
expect(82).to(beLessThan(50) || beGreaterThan(80))

// passes if actual is either less than 10 or greater than 20
expect(actual).to(satisfyAnyOf(beLessThan(@10), beGreaterThan(@20)))

// can include any number of matchers -- the following will pass
// **be careful** -- too many matchers can be the sign of an unfocused test
expect(@6).to(satisfyAnyOf(equal(@2), equal(@3), equal(@4), equal(@5), equal(@6), equal(@7)))

Note: This matcher allows you to chain any number of matchers together. This provides flexibility, but if you find yourself chaining many matchers together in one test, consider whether you
could instead refactor that single test into multiple, more precisely focused tests for better coverage.

Writing Your Own Matchers

In Nimble, matchers are Swift functions that take an expected value and return a MatcherFunc closure. Take equal, for example:

// Swift

public func equal<T: Equatable>(expectedValue: T?) -> MatcherFunc<T?> {
  return MatcherFunc { actualExpression, failureMessage in
    failureMessage.postfixMessage = "equal <\(expectedValue)>"
    return actualExpression.evaluate() == expectedValue
  }
}

The return value of a MatcherFunc closure is a Bool that indicates whether the actual value matches the expectation: true if it does, or false if it doesn't.

The actual equal matcher function does not match when either actual or expected are nil; the example above has been edited for brevity.

Since matchers are just Swift functions, you can define them anywhere: at the top of your test file, in a file shared by all of your tests, or in an Xcode project you distribute to others.

If you write a matcher you think everyone can use, consider adding it to Nimble's built-in set of matchers by sending a pull request! Or distribute it yourself via GitHub.

For examples of how to write your own matchers, just check out the Matchers directory to see how Nimble's built-in set of matchers are implemented. You can also check out the tips below.

Lazy Evaluation

actualExpression is a lazy, memoized closure around the value provided to the expect function. The expression can either be a closure or a value directly passed to expect(...). In order to determine whether that value matches, custom matchers should call actualExpression.evaluate():

// Swift

public func beNil<T>() -> MatcherFunc<T?> {
  return MatcherFunc { actualExpression, failureMessage in
    failureMessage.postfixMessage = "be nil"
    return actualExpression.evaluate() == nil
  }
}

In the above example, actualExpression is not nil--it is a closure that returns a value. The value it returns, which is accessed via the evaluate() method, may be nil. If that value is nil, the beNil matcher function returns true, indicating that the expectation passed.

Use expression.isClosure to determine if the expression will be invoking a closure to produce its value.

Type Checking via Swift Generics

Using Swift's generics, matchers can constrain the type of the actual value passed to the expect function by modifying the return type.

For example, the following matcher, haveDescription, only accepts actual values that implement the Printable protocol. It checks their description against the one provided to the matcher function, and passes if they are the same:

// Swift

public func haveDescription(description: String) -> MatcherFunc<Printable?> {
  return MatcherFunc { actual, failureMessage in
    return actual.evaluate().description == description
  }
}

Customizing Failure Messages

By default, Nimble outputs the following failure message when an expectation fails:

expected to match, got <\(actual)>

You can customize this message by modifying the failureMessage struct from within your MatcherFunc closure. To change the verb "match" to something else, update the postfixMessage property:

// Swift

// Outputs: expected to be under the sea, got <\(actual)>
failureMessage.postfixMessage = "be under the sea"

You can change how the actual value is displayed by updating failureMessage.actualValue. Or, to remove it altogether, set it to nil:

// Swift

// Outputs: expected to be under the sea
failureMessage.actualValue = nil
failureMessage.postfixMessage = "be under the sea"

Supporting Objective-C

To use a custom matcher written in Swift from Objective-C, you'll have to extend the NMBObjCMatcher class, adding a new class method for your custom matcher. The example below defines the class method +[NMBObjCMatcher beNilMatcher]:

// Swift

extension NMBObjCMatcher {
  public class func beNilMatcher() -> NMBObjCMatcher {
    return NMBObjCMatcher { actualBlock, failureMessage, location in
      let block = ({ actualBlock() as NSObject? })
      let expr = Expression(expression: block, location: location)
      return beNil().matches(expr, failureMessage: failureMessage)
    }
  }
}

The above allows you to use the matcher from Objective-C:

// Objective-C

expect(actual).to([NMBObjCMatcher beNilMatcher]());

To make the syntax easier to use, define a C function that calls the class method:

// Objective-C

FOUNDATION_EXPORT id<NMBMatcher> beNil() {
  return [NMBObjCMatcher beNilMatcher];
}

Properly Handling `nil` in Objective-C Matchers

When supporting Objective-C, make sure you handle nil appropriately. Like Cedar, most matchers do not match with nil. This is to bring prevent test writers from being surprised by nil values where they did not expect them.

Nimble provides the beNil matcher function for test writer that want to make expectations on nil objects:

// Objective-C

expect(nil).to(equal(nil)); // fails
expect(nil).to(beNil());    // passes

If your matcher does not want to match with nil, you use NonNilMatcherFunc and the canMatchNil constructor on NMBObjCMatcher. Using both types will automatically generate expected value failure messages when they're nil.

public func beginWith<S: SequenceType, T: Equatable where S.Generator.Element == T>(startingElement: T) -> NonNilMatcherFunc<S> {
    return NonNilMatcherFunc { actualExpression, failureMessage in
        failureMessage.postfixMessage = "begin with <\(startingElement)>"
        if let actualValue = actualExpression.evaluate() {
            var actualGenerator = actualValue.generate()
            return actualGenerator.next() == startingElement
        }
        return false
    }
}

extension NMBObjCMatcher {
    public class func beginWithMatcher(expected: AnyObject) -> NMBObjCMatcher {
        return NMBObjCMatcher(canMatchNil: false) { actualExpression, failureMessage in
            let actual = actualExpression.evaluate()
            let expr = actualExpression.cast { $0 as? NMBOrderedCollection }
            return beginWith(expected).matches(expr, failureMessage: failureMessage)
        }
    }
}

Installing Nimble

Nimble can be used on its own, or in conjunction with its sister project, Quick. To install both Quick and Nimble, follow the installation instructions in the Quick README.

Nimble can currently be installed in one of two ways: using CocoaPods, or with git submodules.

Installing Nimble as a Submodule

To use Nimble as a submodule to test your iOS or OS X applications, follow these 4 easy steps:

Clone the Nimble repository
Add Nimble.xcodeproj to the Xcode workspace for your project
Link Nimble.framework to your test target
Start writing expectations!

For more detailed instructions on each of these steps, read How to Install Quick. Ignore the steps involving adding Quick to your project in order to install just Nimble.

Installing Nimble via CocoaPods

To use Nimble in CocoaPods to test your iOS or OS X applications, add Nimble to your podfile and add the use_frameworks! line to enable Swift support for CocoaPods.

platform :ios, '8.0'

source 'https://github.com/CocoaPods/Specs.git'

# Whatever pods you need for your app go here

target 'YOUR_APP_NAME_HERE_Tests', :exclusive => true do
  use_frameworks!
  pod 'Nimble', '~> 3.1.0'
end

Finally run pod install.

Using Nimble without XCTest

Nimble is integrated with XCTest to allow it work well when used in Xcode test bundles, however it can also be used in a standalone app. After installing Nimble using one of the above methods, there are two additional steps required to make this work.

Create a custom assertion handler and assign an instance of it to the global NimbleAssertionHandler variable. For example:

class MyAssertionHandler : AssertionHandler {
    func assert(assertion: Bool, message: FailureMessage, location: SourceLocation) {
        if (!assertion) {
            print("Expectation failed: \(message.stringValue)")
        }
    }
}

// Somewhere before you use any assertions
NimbleAssertionHandler = MyAssertionHandler()

Add a post-build action to fix an issue with the Swift XCTest support library being unnecessarily copied into your app

Edit your scheme in Xcode, and navigate to Build -> Post-actions
Click the "+" icon and select "New Run Script Action"
Open the "Provide build settings from" dropdown and select your target
Enter the following script contents:

rm "${SWIFT_STDLIB_TOOL_DESTINATION_DIR}/libswiftXCTest.dylib"

You can now use Nimble assertions in your code and handle failures as you see fit.

License

john-langley/Nimble

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