fixes behavior of inverted expectations which can fulfill after timeout

Author: brennanMKE

Package.swift

@@ -27,7 +27,6 @@ let package = Package(
             swiftSettings: nil,
             linkerSettings: [.linkedFramework("XCTest")]
         ),
-        
         .testTarget(
             name: "AsyncTestingTests",
             dependencies: ["AsyncTesting"],

Sources/AsyncTesting/AsyncExpectation.swift

@@ -34,14 +34,20 @@ public actor AsyncExpectation {
         self.isInverted = isInverted
         self.expectedFulfillmentCount = expectedFulfillmentCount
     }
-    
+
+    /// Marks the expectation as having been met.
+    ///
+    /// It is an error to call this method on an expectation that has already been fulfilled,
+    /// or when the test case that vended the expectation has already completed.
     public func fulfill(file: StaticString = #filePath, line: UInt = #line) {
         guard state != .fulfilled else { return }
-        
-        guard !isInverted else {
-            XCTFail("Inverted expectation fulfilled: \(expectationDescription)", file: file, line: line)
-            state = .fulfilled
-            finish()
+
+        if isInverted {
+            if state != .timedOut {
+                XCTFail("Inverted expectation fulfilled: \(expectationDescription)", file: file, line: line)
+                state = .fulfilled
+                finish()
+            }
             return
         }
 
@@ -70,7 +76,9 @@ public actor AsyncExpectation {
 
     internal func timeOut(file: StaticString = #filePath,
                           line: UInt = #line) async {
-        if state != .fulfilled && !isInverted {
+        if isInverted {
+            state = .timedOut
+        } else if state != .fulfilled {
             state = .timedOut
             XCTFail("Expectation timed out: \(expectationDescription)", file: file, line: line)
         }

Tests/AsyncTestingTests/AsyncTestingTests.swift

@@ -1,6 +1,34 @@
 import XCTest
 @testable import AsyncTesting
 
+actor AsyncRunner {
+    typealias VoidNeverContinuation = CheckedContinuation<Void, Never>
+    private var continuations: [VoidNeverContinuation] = []
+
+    public func run(timeout: Double = 5.0) async {
+        await withTaskCancellationHandler {
+            Task {
+                await finish()
+            }
+        } operation: {
+            await withCheckedContinuation {
+                continuations.append($0)
+            }
+            Task {
+                try await Task.sleep(seconds: timeout)
+                finish()
+            }
+        }
+    }
+
+    public func finish() {
+        while !continuations.isEmpty {
+            let continuation = continuations.removeFirst()
+            continuation.resume(returning: ())
+        }
+    }
+}
+
 final class AsyncExpectationTests: XCTestCase {
 
     func testDoneExpectation() async throws {
@@ -42,6 +70,23 @@ final class AsyncExpectationTests: XCTestCase {
         task.cancel()
         try await waitForExpectations([notDone], timeout: delay * 2)
     }
+
+    func testNotYetDoneAndThenDoneExpectation() async throws {
+        let delay = 0.01
+        let notYetDone = asyncExpectation(description: "not yet done", isInverted: true)
+        let done = asyncExpectation(description: "done")
+
+        let task = Task {
+            await AsyncRunner().run()
+            XCTAssertTrue(Task.isCancelled)
+            await notYetDone.fulfill() // will timeout before being called
+            await done.fulfill() // will be called after cancellation
+        }
+
+        try await waitForExpectations([notYetDone], timeout: delay)
+        task.cancel()
+        try await waitForExpectations([done])
+    }
 
     func testDoneAndNotDoneInvertedExpectation() async throws {
         let delay = 0.01
@@ -91,5 +136,5 @@ final class AsyncExpectationTests: XCTestCase {
 
         try await waitForExpectations([one, two, three])
     }
-    
+
 }