### Question:
NeovimBufferRxWrapper implements NeovimBufferRxApi { @Override public Single<Boolean> attach(boolean loadFullBufferOnStart, Map opts) { return Single.fromFuture(neovimBufferApi.attach(loadFullBufferOnStart, opts)); } NeovimBufferRxWrapper(NeovimBufferApi neovimBufferApi); @Override Buffer get(); @Override Single<Integer> getLineCount(); @Override Single<List<String>> getLines(int start, int end, boolean strictIndexing); @Override Completable setLines(int start, int end, boolean strictIndexing, List<String> replacement); @Override Single<Integer> getOffset(int index); @Override Single<Object> getVar(String name); @Override Completable deleteVar(String name); @Override Completable setVar(String name, Object value); @Override Single<Object> getOption(String name); @Override Completable setOption(String name, Object value); @Override Single<Integer> getNumber(); @Override Single<String> getName(); @Override Completable setName(String name); @Override Single<Boolean> isLoaded(); @Override Single<Boolean> isValid(); @Override Single<VimCoords> getMark(String name); @Override Single<Object> getChangedTick(); @Override Single<List<VimKeyMap>> getKeymap(String mode); @Override Completable setKeymap(String mode, String lhs, String rhs, Map<String, Boolean> options); @Override Completable deleteKeymap(String mode, String lhs); @Override Single<Integer> addHighlight(int srcId, String hlGroup, int line, int colStart, int colEnd); @Override Completable clearHighlight(int srcId, int lineStart, int lineEnd); @Override Completable clearNamespace(int namespaceId, int lineStart, int lineEnd); @Override Single<Integer> setVirtualText(int namespaceId, int line, List<HighlightedText> chunks, Map optionalParams); @Override Single<Boolean> attach(boolean loadFullBufferOnStart, Map opts); @Override Single<Boolean> detach(); @Override Single<Map<String, CommandInfo>> getCommands(GetCommandsOptions commandsOptions);  }### Answer:
@Test public void delegatesAttach() { var opts = Map.of(); given(neovimBufferApi.attach(false, opts)).willReturn(CompletableFuture.completedFuture(true)); neovimBufferRxWrapper.attach(false, opts) .test() .assertComplete() .assertNoErrors() .assertValue(true); verify(neovimBufferApi).attach(false, opts); }