标签： JUnit

有时候，需要对一些异步方法进行单元测试（尽管不推荐这样做），传统的assert只能在调用线程抛出AssertException，而测试框架往往只能监测主线程上的AssertException（JUnit），所以需要在主线程上等待异步调用结束，再去assert结果。

利用Java8的CompletableFuture，我们可以很方便地做到这一点，代码如下所示：

public class AsyncTestHelper<T> {
    private CompletableFuture<T> mFuture = new CompletableFuture<>();

    public CompletableFuture<T> getFuture() {
        return mFuture;
    }

    public void assertBlock(Callable<T> callable) {
        try {
            T result = callable.call();
            complete(result);
        } catch (Throwable e) {
            completeExceptionally(e);
        }
    }

    public void complete(T value) {
        mFuture.complete(value);
    }

    public void completeExceptionally(Throwable throwable) {
        mFuture.completeExceptionally(throwable);
    }

    public T waitForCompletion() throws Throwable {
        return waitForCompletion(0);
    }

    public T waitForCompletion(int timeout) throws Throwable {
        T result = null;
        try {
            if (timeout <= 0) {
                result = mFuture.get();
            } else {
                result = mFuture.get(timeout 
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 , TimeUnit.MILLISECONDS);
            }
        } catch (Throwable ex) {
            if (ex instanceof ExecutionException) {
                throw ex.getCause();
            } else {
                throw ex;
            }
        }
        return result;
    }
}

使用例子如下所示：

@Test
public void assertGetDeviceInfo() throws Throwable {
    XLinkCoreDevice nullDevice = createTestDevice();

    final AsyncTestHelper<XLinkCoreDeviceInfo> helper = new AsyncTestHelper<>();
    XLinkCoreSDK.getInstance().getDeviceInfo(
            nullDevice,
            new XLinkCoreSDK.Callback<XLinkCoreDeviceInfo>() {
                @Override
                public void onSuccess(final XLinkCoreDeviceInfo result) {
                    println("onSuccess() called with: result = [" + result + "]");
                    // 异步回调
                    helper.assertBlock(new Callable<XLinkCoreDeviceInfo>() {
                        @Override
                        public XLinkCoreDeviceInfo call() throws Exception {
                            assertEquals(true, result.isBound());
                            assertEquals(5, result.getProtocolVersion());
                            assertArrayEquals(ByteUtil.hexToBytes(TEST_DEVICE_MAC), result.getMac());
                            assertEquals(TEST_DEVICE_PRODUCT_ID, result.getPid());
                            return result;
                        }
                    });
                }

                @Override
                public void onFail(XLinkCoreException exception) {
                    println("onFail() called with: exception = [" + exception + "]");
                    helper.completeExceptionally(exception);
                }
            }
    );
    helper.waitForCompletion(); // 等待结果，并抛出原有的Exception
}

欢迎提出任何建议~