iOS implementation of .NET Issue 449 unit test

Replication_Tests.m

- (void)test18_pushAttachmentToCouchDB {
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:@"http://localhost:5984/issue449"]];
    request.HTTPMethod = @"DELETE";
    NSHTTPURLResponse *response = nil;
    [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];
    Assert(response.statusCode == 200 || response.statusCode == 404);
    
    request.HTTPMethod = @"PUT";
    [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];
    Assert(response.statusCode == 201);
    
    CBLReplication *push = [db createPushReplication:request.URL];
    [self createDocuments:2];
    CBLDocument *attachDoc = [db createDocument];
    [attachDoc update:^BOOL(CBLUnsavedRevision * __nonnull rev) {
        NSMutableDictionary *props = [rev.userProperties mutableCopy];
        props[@"foo"] = @"bar";
        [rev setUserProperties:props];
        NSUInteger size = 50 * 1024;
        unsigned char attachbytes[size];
        for (NSUInteger i = 0; i < size; i++) {
            attachbytes[i] = 1;
        }
        NSData* attachment = [NSData dataWithBytes: attachbytes length: size];
        [rev setAttachmentNamed: @"myattachment"
                   withContentType: @"text/plain; charset=utf-8"
                           content: attachment];
        
        return YES;
    } error:nil];
    
    [self runReplication:push expectedChangesCount:3];
    attachDoc = [db existingDocumentWithID:attachDoc.documentID];
    [attachDoc update:^BOOL(CBLUnsavedRevision * __nonnull rev) {
        NSMutableDictionary *props = [rev.userProperties mutableCopy];
        props[@"extraminutes"] = @"5";
        [rev setUserProperties:props];
        return YES;
    } error:nil];
    
    push = [db createPushReplication:push.remoteURL];
    [self runReplication:push expectedChangesCount:1];
    
    [db close:nil];
    [self eraseTestDB];
    CBLReplication *pull = [db createPullReplication:push.remoteURL];
    [self runReplication:pull expectedChangesCount:3];
    AssertEq(db.documentCount, 3UL);
    attachDoc = [db existingDocumentWithID:attachDoc.documentID];
    Assert(attachDoc != nil);
    Assert(attachDoc.currentRevision.attachments != nil);
    [attachDoc update:^BOOL(CBLUnsavedRevision * __nonnull rev) {
        NSMutableDictionary *props = [rev.userProperties mutableCopy];
        props[@"extraminutes"] = @"10";
        [rev setUserProperties:props];
        return YES;
    } error:nil];
    
    push = [db createPushReplication:pull.remoteURL];
    [self runReplication:push expectedChangesCount:1];
    AssertNil(push.lastError);
}