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GitHub - bastos/Nimble: A Matcher Framework for Swift and Objective-C

A Matcher Framework for Swift.

Setup

Currently, you must add this project as a subproject and link against the Nimble.framework.

Usage

Matchers follow Cedar's design. They're generic-based:

import Nimble
// ...
expect(1).to(equal(1))
expect(1.2).to(beCloseTo(1.1, within: 1))

Certain operators work as expected too:

expect("foo") != "bar"
expect(10) > 2

The expect function autocompletes to include file: and line:, but these are optional. The defaults will populate the current file and line.

Also, expect takes a lazily computed value. This makes it possible to handle exceptions in-line (even though Swift doesn't support exceptions):

var exception = NSException(name: "laugh", reason: "Lulz", userInfo: nil)
expect(exception.raise()).to(raiseException(named: "laugh"))

Or you can use trailing-closure style as needed:

expect {
    "hello"
}.to(equalTo("hello"))

C primitives are allowed without any wrapping:

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

In fact, type inference is used to remove redudant type specifying:

// both work
expect(1 as CInt).to(equal(1))
expect(1).to(equal(1 as CInt))

Asynchronous Expectations

Simply exchange to and toNot with toEventually and toEventuallyNot:

var value = 0
dispatch_async(dispatch_get_main_queue()) {
    value = 1
}
expect(value).toEventually(equal(1))

This polls the expression inside expect(...) until the given expectation succeeds within a 1 second. You can explicitly pass the timeout parameter:

expect(value).toEventually(equal(1), timeout: 1)

If you prefer the callback-style that some testing frameworks do, use waitUntil:

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

And like the other asynchronous expectation, an optional timeout period can be provided:

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

List of Builtin Matchers

The following matchers are currently included with Nimble:

  • equal(expectedValue) (also == and != operators). Values must be Equatable, Comparable, or NSObjects.
  • beCloseTo(expectedValue, within: Double = 0.0001). Values must be coercable into a Double.
  • beLessThan(upperLimit) (also < operator). Values must be Comparable.
  • beLessThanOrEqualTo(upperLimit) (also <= operator). Values must be Comparable.
  • beGreaterThan(lowerLimit) (also > operator). Values must be Comparable.
  • beGreaterThanOrEqualTo(lowerLimit) (also >= operator). Values must be Comparable,
  • raiseException() Matches if the given closure raises an exception.
  • raiseException(#named: String?) Matches if the given closure raises an exception with the given name.
  • raiseException(#named: String?, #reason: String?) Matches if the given closure raises an exception with the given name and reason.
  • beNil() Matches if the given value is nil.
  • beTruthy(): Matches if the given value is not nil (for optionals) or false (for LogicValue supported types like bool). Optional Bools are automatically unwrapped first.
  • beFalsy(): Matches if the given value is nil (for optionals) or false (for LogicValue supported types like bool). Optional Bools are automatically unwrapped first.
  • contain(items: T...) Matches if all of items are in the given container. Valid containers are Swift collections that have Equatable elements; NSArrays and NSSets; and Strings - which use substring matching.
  • beginWith(starting: T) Matches if starting is in beginning the given container. Valid containers are Swift collections that have Equatable elements; NSArrays; and Strings - which use substring matching.
  • endWith(ending: T) Matches if ending is at the end of the given container. Valid containers are Swift collections that have Equatable elements; NSArrays; and Strings - which use substring matching.
  • beIdenticalTo(expectedInstance: T) (also === and !== operators) Matches if expectedInstance has the same pointer address (identity equality) with the given value. Only works with Objective-C compatible objects.
  • beAnInstanceOf(expectedClass: Class) Matches if the given object is the expectedClass using isMemberOfClass:. Only works with Objective-C compatible objects.
  • beAKindOf(expectedClass: Class) Matches if the given object is the expectedClass using isKindOfClass:. Only works with Objective-C compatible objects.
  • beEmpty() Matches if the given type contains nothing. Works with Strings and Collections from both Swift and Objective-C

Objective-C

Want to use this for Objective-C? The same syntax applies except you must use Objective-C objects:

#import <Nimble/Nimble.h>
// ...
expect(@1).to(equal(@1));
expect(@1.2).to(beCloseTo(@1.3).within(@0.5));
expect(@[@1, @2]).to(contain(@1));

For exceptions, use expectAction, which ignores the expression returned:

expectAction([exception raise]).to(raiseException());

Writing Your Own Matchers

Most matchers can be defined using MatcherFunc:

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

The return value inside MatcherFunc closure is a Bool that indicates success or failure to match.

actualExpression is a lazy, memoized closure around the value provided to expect(...).

Using Swift's generics, matchers can constrain the type of the actual value received from expect(<actualValue>) by modifying the return type:

@objc protocol FuzzyThing { } // @objc for objc support (see Objective-C section below)
// Only expect(fuzzyObject).to(beFuzzy()) is allowed by the compiler,
// where fuzzyObject supports the FuzzyThing protocol or is nil.
func beFuzzy() -> MatcherFunc<FuzzyThing?> {
    return MatcherFunc { actualExpression, failureMessage in
        // ...
    }
}

Customizing Failure Messages

failureMessage is a structure of the final expectation message to emit. If you want to suppress emitting the actual value, you can nil out actualValue in your matcher:

failureMessage.actualValue = nil
failureMessage.postfixMessage = "yo"
// resulting error: expected to yo

Supporting Objective-C

Since Swift generics cannot interop with Objective-C, you need to wrap your matchers and expose them as regular C-functions. The common location is to place them in NMBObjCMatcher:

// Swift
extension NMBObjCMatcher {
    class func beFuzzyMatcher() -> NMBObjCMatcher {
        return NMBObjCMatcher { actualBlock, failureMessage, location in
            let expr = Expression(expression: ({ actualBlock() as FuzzyThing? }), location: location)
            return beFuzzy().matches(expr, failureMessage: failureMessage)
        }
    }
}

Afterwards, you'll probably want a nice interface for usage:

// Objective-C
FOUNDATION_EXPORT id<NMBMatcher> beFuzzy() {
    return [NMBObjCMatcher beFuzzyMatcher];
}

When supporting Objective-C, make sure you handle nil appropriately. Like Cedar, most matchers do not match with nil. This is to prevent accidental nil-fallthroughs:

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

Which beNil() allows for explicit resolution:

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