}

    @Test
    @DisplayName("readLine(): reads until newline and handles CRLF")
    void readLine_reads() throws Exception {
        SmbRandomAccessFile raf = spy(newInstance("r", false, false, false));
        // Sequence: 'a','b','\r','\n','c','\n'
        when(raf.read()).thenReturn((int) 'a', (int) 'b', (int) '\r', (int) '\n');
        assertEquals("ab", raf.readLine());

        assertArgumentNotNull("reader", reader);
        this.reader = reader;
    }

    @Override
    public boolean hasNext() {
        if (line == EMPTY) {
            line = ReaderUtil.readLine(reader);
        }
        return line != null;
    }

    @Override
    public String next() {
        if (!hasNext()) {
            throw new NoSuchElementException();
        }

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 de prueba, solo para tus tests.

### Usa el atributo `app.dependency_overrides`

                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) {

  @Override
  float readFloat();

  @CanIgnoreReturnValue // to skip some bytes
  @Override
  double readDouble();

  @CanIgnoreReturnValue // to skip a line
  @Override
  @Nullable String readLine();

  @CanIgnoreReturnValue // to skip a field
  @Override
  String readUTF();

        } else {
          System.err.println(callback.prompt)
          callback.password =
            System.`in`
              .bufferedReader()
              .readLine()
              .toCharArray()
        }
      } else {
        throw UnsupportedCallbackException(callback)
      }
    }
  }
}

fun main() {
  YubikeyClientAuth().run()

                this.getClass().getClassLoader().getResourceAsStream("suggest_indices/suggest/mappings-default.json")))) {

            String line;
            while ((line = br.readLine()) != null) {
                mappingSource.append(line);
            }
        }
        return mappingSource.toString();
    }

    private String getDefaultIndexSettings() throws IOException {

            final RobotsTxt robotsTxt = new RobotsTxt();
            final List<Directive> currentDirectiveList = new ArrayList<>();
            boolean isGroupRecordStarted = false;
            while ((line = reader.readLine()) != null) {
                line = stripComment(line).trim();
                if (StringUtil.isEmpty(line)) {
                    continue;
                }

                new BufferedReader(new InputStreamReader(this.getClass().getClassLoader().getResourceAsStream(getSuggestAnalyzerPath())))) {

            String line;
            while ((line = br.readLine()) != null) {
                sb.append(line);
            }
        }
        return sb.toString().replaceAll(Pattern.quote("${fess.dictionary.path}"), dictionaryPath);
    }

    /**

     */
    @Override
    public void run() {
        boolean running = true;
        while (running) {
            try {
                final String line = br.readLine();
                if (line == null) {
                    running = false;
                } else {
                    if (logger.isDebugEnabled()) {
                        logger.debug(line);
                    }