[SR-1110] Add convenience XCTestExpectation constructors for NSPredicate

[modocache]

Previous ID	SR-1110
Radar	None
Original Reporter	@modocache
Type	New Feature
Status	Closed
Resolution	Done

Attachment: Download

Additional Detail from JIRA

Votes	0
Component/s	XCTest
Labels	New Feature, StarterBug
Assignee	apps.yoon (JIRA)
Priority	Medium

md5: 80de972c44d4ad944e39eb5cd68136b2

Issue Description:

Apple XCTest offers several convenient methods for constructing XCTestExpectations:

@interface XCTestCase : XCTest
// ...
- (XCTestExpectation *)keyValueObservingExpectationForObject:(id)objectToObserve keyPath:(NSString *)keyPath expectedValue:(nullable id)expectedValue;
- (XCTestExpectation *)keyValueObservingExpectationForObject:(id)objectToObserve keyPath:(NSString *)keyPath handler:(nullable XCKeyValueObservingExpectationHandler)handler;
- (XCTestExpectation *)expectationForNotification:(NSString *)notificationName object:(nullable id)objectToObserve handler:(nullable XCNotificationExpectationHandler)handler;
- (XCTestExpectation *)expectationForPredicate:(NSPredicate *)predicate evaluatedWithObject:(id)object handler:(nullable XCPredicateExpectationHandler)handler;
// ...
@end

Key-value observing doesn't exist in native Swift, but NSNotification and NSPredicate do (thanks to swift-corelibs-foundation). swift-corelibs-xctest already defines a constructor for NSNotification: https://github.com/yoonapps/swift-corelibs-xctest/blob/c2a9258c7c17e32bf9082709ef111e59aba86a95/Sources/XCTest/XCTestCase.swift#L324. This was added in #85

Add the constructor for NSPredicate: -[XCTestCase expectationForPredicate:evaluatedWithObject:handler:].

Also, note that you'll need to add the following closure typealias as well: typedef BOOL (^XCPredicateExpectationHandler)();.

https://bugs.swift.org/browse/SR-907 is a great reference on how to approach this task.

[modocache]

This task is blocked until swift-corelibs-foundation implements NSPredicate. See: swiftlang/swift-corelibs-foundation#127

[modocache]

swiftlang/swift-corelibs-foundation#127 was merged! apps.yoon (JIRA User), do you still want to take this on?

[swift-ci]

Comment by Kyle Yoon (JIRA)

@modocache Sure thing! Assigning to myself.

[swift-ci]

Comment by Kyle Yoon (JIRA)

@modocache Could I get you thoughts on my implementation:

Since `expectation(forPredicate...)` needs to re-evaluate the predicate periodically, and `waitForExpectations(...)` runs a loop to check if the expectation `isFulfilled`, I make a subclass of `XCTestExpectation` that:

• holds the predicate and the object with which to evaluate it

• overrides `isFulfilled` to evaluate the predicate.

Would you be against adding this subclass?

[modocache]

I think a subclass sounds fine--in fact, I think Apple's XCTest uses a subclass. I don't think it overrides isFulfilled, though. Instead, it probably re-evaluates the predicate periodically, probably using a timer or something.

But that aside, I'd be fine with pretty much any working implementation, even one that overrides isFulfilled. Because XCTest has such a robust suite of tests, I think anything that works is a great step forward--we can find room to refactor the implementation at a later time.

By the way, have you seen this FIXME? Perhaps using a runloop source that could be signaled would make it easier to implement this? If not no worries, just a heads up.

[swift-ci]

Comment by Kyle Yoon (JIRA)

@modocache
Is there a way to pass the memory address of an object declared in a functional test to // CHECK:?
I've tried using string interpolation and unsafeAddress(of🙂 but haven't had any luck.

[swift-ci]

Comment by Kyle Yoon (JIRA)

I've tried using the regex ^0x[0-9A-Fa-f]{1,16}$ but I'm getting the error "Actual line did not match the regular expression".

Full line:

// CHECK: .*/Tests/Functional/Asynchronous/Predicates/Expectations/main.swift:34: error: PredicateExpectationsTestCase.test_immediatelyFalsePredicateAndObject_fails : Asynchronous wait failed - Exceeded timeout of 0.1 seconds, with unfulfilled expectations: Expect `<NSPredicate: ^0x[0-9A-Fa-f]\{1,16\}$>` for object <NSObject: ^0x[0-9A-Fa-f]\{1,16\}$>

[modocache]

apps.yoon (JIRA User): \^ matches the beginning of a line, $ matches the end of a line. Your regular expression would match if the entire line was just a memory address, but not if the line contained a memory address. Have you tried just 0x[0-9A-Fa-f]{1,16}, without the \^$?

[swift-ci]

Comment by Kyle Yoon (JIRA)

@modocache I've been getting linker errors and have not been able to get a build going. Do you mind taking a look at the ? I can't figure out what I screwed up :/

Ignore that 😃 sorry!

[swift-ci]

Comment by Kyle Yoon (JIRA)

And yes, your regex fix worked. Thank you!