// part of the line returned by ReadLine.
func (b *Reader) ReadLine() (line []byte, isPrefix bool, err error) {
	line, err = b.ReadSlice('\n')
	if err == ErrBufferFull {
		// Handle the case where "\r\n" straddles the buffer.
		if len(line) > 0 && line[len(line)-1] == '\r' {
			// Put the '\r' back on buf and drop it from line.
			// Let the next call to ReadLine check for "\r\n".
			if b.r == 0 {

func (b *Buffer) ReadBytes(delim byte) (line []byte, err error) {
	slice, err := b.readSlice(delim)
	// return a copy of slice. The buffer's backing array may
	// be overwritten by later calls.
	line = append(line, slice...)
	return line, err
}

// readSlice is like ReadBytes but returns a reference to internal buffer data.
func (b *Buffer) readSlice(delim byte) (line []byte, err error) {
	i := IndexByte(b.buf[b.off:], delim)

  /** Read a single line counted against the header size limit. */
  fun readLine(): String {
    val line = source.readUtf8LineStrict(headerLimit)
    headerLimit -= line.length.toLong()
    return line
  }

  /** Reads headers or trailers. */
  fun readHeaders(): Headers {
    val result = Headers.Builder()
    while (true) {
      val line = readLine()
      if (line.isEmpty()) break
      result.addLenient(line)
    }

      return reader.readLine();
    } catch (Throwable e) {
      throw closer.rethrow(e);
    } finally {
      closer.close();
    }
  }

  /**
   * Reads all the lines of this source as a list of strings. The returned list will be empty if
   * this source is empty.
   *
   * <p>Like {@link BufferedReader#readLine()}, this method considers a line to be a sequence of

            String line = br.readLine();
            while (line != null) {
                lineNumber++;
                gatherDeadUserGuideLinksInLineReleaseNotes(sourceFile, line, lineNumber, errorsForFile);
                gatherDeadJavadocLinksInLineReleaseNotes(sourceFile, line, lineNumber, errorsForFile);

                line = br.readLine();
            }
        } catch (IOException e) {

    BufferedReader r = new BufferedReader(getChunkedReader(input, chunk));
    List<String> lines = new ArrayList<>();
    String line;
    while ((line = r.readLine()) != null) {
      lines.add(line);
    }
    r.close();
    return lines;
  }

  private static List<String> readUsingReader(String input, int chunk, boolean asReader)
      throws IOException {

    DataInput in = new LittleEndianDataInputStream(new ByteArrayInputStream(data));
    UnsupportedOperationException expected =
        assertThrows(UnsupportedOperationException.class, in::readLine);
    assertThat(expected).hasMessageThat().isEqualTo("readLine is not supported");
  }

  public void testReadLittleEndian() throws IOException {
    DataInput in = new LittleEndianDataInputStream(new ByteArrayInputStream(data));

        ByteStreams.newDataInput(
            "This is a line\r\nThis too\rand this\nand also this".getBytes(UTF_8));
    assertThat(in.readLine()).isEqualTo("This is a line");
    assertThat(in.readLine()).isEqualTo("This too");
    assertThat(in.readLine()).isEqualTo("and this");
    assertThat(in.readLine()).isEqualTo("and also this");
  }

  public void testNewDataInput_readFloat() {

                Thread.currentThread().getContextClassLoader().getResourceAsStream("suggest_settings/default-badwords.txt")))) {

            String line;
            while ((line = br.readLine()) != null) {
                if (line.length() > 0 && !line.startsWith("#")) {
                    list.add(line.trim());
                }
            }
        } catch (final Exception e) {

Probablemente quieras probar el proveedor externo una vez, pero no necesariamente llamarlo para cada test que se realice.

En este caso, puedes sobrescribir la dependencia que llama a ese proveedor y usar una dependencia personalizada que devuelva un usuario mock, solo para tus tests.