Fixed library tests

According to the below link some test assertions are now not available. Made substitute extensions.
ReactiveX/RxJava#6526

rxandroidble/src/test/groovy/com/polidea/rxandroidble2/extensions/TestSubscriberExtension.groovy

@@ -50,6 +50,26 @@ class TestSubscriberExtension {
  subscriber.assertValueSequence(values)
  }
 
+ static <T> void assertTerminated(final TestObserver<T> subscriber) {
+ try {
+ subscriber.assertComplete()
+ } catch (Throwable ignored) {
+ subscriber.assertError({ true })
+ }
+ }
+
+ static <T> void assertNotTerminated(final TestObserver<T> subscriber) {
+ subscriber.assertNotComplete()
+ subscriber.assertNoErrors()
+ if (subscriber.isDisposed()) {
+ throw AssertionError("TestObserver is disposed")
+ }
+ }
+
+ static <T> void assertErrorMessage(final TestObserver<T> subscriber, final String errorMessage) {
+ subscriber.assertError { it.message == errorMessage }
+ }
+
  static boolean assertAllBatchesSmaller(final TestSubscriber<byte[]> subscriber, int maxBatchSize) {
  def emittedValues = subscriber.values()
  def size = emittedValues.size()