function testCheckConnection_Self() {
  connectionTest_setUp();
  var block = {type_: "test block"};
  input.sourceBlock_ = block;
  try {
    input.checkConnection_(input);
    fail();
  } catch (e) {
    // expected
  }

  connectionTest_tearDown();
}
The next set of tests checks that exceptions are being thrown at the correct
times (external view of errors).