Test case to check if receiver blocks on empty channel, and resumes on close.

[kavyasrinet]

No description provided.

[wangkuiyi]

10 is a magical number

[kavyasrinet]

Thank you for the review.
I just realized that we already checked in the test cases : BufferedChannelCloseUnblocksReceiversTest and UnbufferedChannelCloseUnblocksReceiversTest that perform these operations already.
In that case, this PR would be redundant and maybe I can close it.

[wangkuiyi]

5 is a magical number

[wangkuiyi]

unnecessary comment

[wangkuiyi]

The prefix Test is a convention of unit test names. This function is not a unit test; a better name could be ReceiveFromEmptyChannelShouldBlock.

[wangkuiyi]

A rewrite is as follows:

void ReceiveFromEmptyChannelShouldBlockAndCloseUnblocksIt(Channel *ch) {
  bool received = false;
  std::thread t([&]() {
    int out;
    ch->Receive(&out);  // should block since channel is empty
    received = true;
  });
  std::this_thread::sleep_for(std::chrono::milliseconds(100));  // wait 0.1 sec
  EXPECT_EQ(received,
            false);  // the receiver should be blocked since channel is empty

  CloseChannel(ch);
  t.join();
  EXPECT_EQ(received,
            true);  // when we close the channel, the receiver should unblock
  delete ch;
}

TEST(Channel, ReceiveFromEmptyBufferedChannelShouldBlockAndCloseUnblocksIt) {
  auto ch = MakeChannel<size_t>(3);  // buffered
  ReceiveFromEmptyChannelShouldBlockAndCloseUnblocksIt(ch);
}

TEST(Channel, ReceiveFromEmptyUnBufferedChannelShouldBlockAndCloseUnblocksIt) {
  auto ch = MakeChannel<size_t>(0);  // unbuffered
  ReceiveEmptyChannelTest(ch);
}