运行单元测试创​​建UIKit对象会导致断点

Question

在运行单元测试时创建UILabel时，会导致 EXC_BREAKPOINT（代码= EXC_i386_BPT，子代码0x0）

我做错了什么？

- (void)setLabelCount:(NSUInteger)labelCount {
    _labelCount = labelCount;
    NSMutableArray *labels = [[NSMutableArray alloc] init];
    for (int idx=0; idx<self.labelCount; idx++) {
        UILabel *lbl = [[UILabel alloc] initWithFrame:CGRectZero];     // <---
        lbl.backgroundColor = [UIColor clearColor];
        [labels addObject:lbl];
        [self.dataView addSubview:lbl];
    }
    self.labels = labels;

    [self updateContents];
}

以下是调用此代码的单元测试

- (void)setUp {
    cell = [[LDPChartCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"ChartCell"];
    cell.labelCount = 10;    // <---
}

- (void)tearDown {
    cell = nil;
}

- (void)testThatReuseIdentifierIsSet {
    STAssertEqualObjects(cell.reuseIdentifier, @"ChartCell", @"");
}