Use a synchroniser combined with states to test expectations that are

satisfied asynchronously.

Tests/Integration/StateMachineTests.m

@@ -15,6 +15,60 @@ - (void)equals:(NSString *)state;
 
 @end
 
+@interface LRSynchroniser : NSObject
+
++ (id)synchroniser;
++ (id)synchroniserWithTimeout:(NSTimeInterval)timeout;
+- (void)waitUntil:(id<LRStatePredicate>)statePredicate;
+
+@end
+
+@implementation LRSynchroniser {
+  NSTimeInterval _timeout;
+}
+
++ (id)synchroniser
+{
+  return [[self alloc] initWithTimeout:5];
+}
+
++ (id)synchroniserWithTimeout:(NSTimeInterval)timeout
+{
+  return [[self alloc] initWithTimeout:timeout];
+}
+
+- (id)initWithTimeout:(NSTimeInterval)timeout
+{
+  self = [super init];
+  if (self) {
+    _timeout = timeout;
+  }
+  return self;
+}
+
+- (void)waitUntil:(id<LRStatePredicate>)statePredicate
+{
+  if ([statePredicate isActive]) return;
+
+  NSDate *waitUntil = [NSDate dateWithTimeIntervalSinceNow:_timeout];
+
+  BOOL predicateSatisfied = NO;
+  NSInteger pollingInterval = 0.1;
+
+  while (!predicateSatisfied) {
+    NSDate *runUntil = [NSDate dateWithTimeIntervalSinceNow:pollingInterval];
+
+    if ([runUntil earlierDate:waitUntil] == waitUntil) {
+      break;
+    }
+    [[NSRunLoop currentRunLoop] runUntilDate:runUntil];
+
+    predicateSatisfied = [statePredicate isActive];
+  }
+}
+
+@end
+
 DEFINE_FUNCTIONAL_TEST_CASE(StateMachineTests) {
   LRMockyStateMachine *readiness;
 }
@@ -86,4 +140,46 @@ - (void)testMultipleExpectationsWithStates
   assertThat(testCase, passed());
 }
 
+- (void)testUsingStatesToTestAsynchronousCode
+{
+  LRSynchroniser *synchroniser = [LRSynchroniser synchroniser];
+
+  [readiness transitionTo:@"waiting"];
+
+  [context check:^{
+    [[expectThat(testObject) receives] doSomething]; [then state:readiness becomes:@"ready"];
+  }];
+
+  dispatch_async(dispatch_get_main_queue(), ^{
+    [testObject doSomething];
+  });
+
+  [synchroniser waitUntil:[readiness equals:@"ready"]];
+  [context assertSatisfied];
+
+  assertThat(testCase, passed());
+}
+
+- (void)testUsingStatesToTestAsynchronousCodeWithTimeout
+{
+  LRSynchroniser *synchroniser = [LRSynchroniser synchroniserWithTimeout:0.3];
+
+  [readiness transitionTo:@"waiting"];
+
+  [context check:^{
+    [[expectThat(testObject) receives] doSomething]; [then state:readiness becomes:@"ready"];
+  }];
+
+  double delayInFractionalSeconds = 0.4;
+  dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInFractionalSeconds * NSEC_PER_SEC);
+  dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
+    [testObject doSomething];
+  });
+
+  [synchroniser waitUntil:[readiness equals:@"ready"]];
+  [context assertSatisfied];
+
+  assertThat(testCase, failedWithNumberOfFailures(1));
+}
+
 END_TEST_CASE