### Question:
TesseractOCRConfig implements Serializable { public void setFilter(String filter) { if (filter.equals(null)) { throw new IllegalArgumentException("Filter value cannot be null. Valid values are point, hermite, " + "cubic, box, gaussian, catrom, triangle, quadratic and mitchell."); } String[] allowedFilters = {"Point", "Hermite", "Cubic", "Box", "Gaussian", "Catrom", "Triangle", "Quadratic", "Mitchell"}; for (int i = 0; i < allowedFilters.length; i++) { if (filter.equalsIgnoreCase(allowedFilters[i])) { this.filter = filter; return; } } throw new IllegalArgumentException("Invalid filter value. Valid values are point, hermite, " + "cubic, box, gaussian, catrom, triangle, quadratic and mitchell."); } TesseractOCRConfig();  TesseractOCRConfig(InputStream is); String getTesseractPath(); void setTesseractPath(String tesseractPath); String getTessdataPath(); void setTessdataPath(String tessdataPath); String getLanguage(); void setLanguage(String language); String getPageSegMode(); void setPageSegMode(String pageSegMode); String getPageSeparator(); void setPageSeparator(String pageSeparator); void setTrustedPageSeparator(String pageSeparator); void setPreserveInterwordSpacing(boolean preserveInterwordSpacing); boolean getPreserveInterwordSpacing(); long getMinFileSizeToOcr(); void setMinFileSizeToOcr(long minFileSizeToOcr); long getMaxFileSizeToOcr(); void setMaxFileSizeToOcr(long maxFileSizeToOcr); void setTimeout(int timeout); int getTimeout(); void setOutputType(OUTPUT_TYPE outputType); void setOutputType(String outputType); OUTPUT_TYPE getOutputType(); int isEnableImageProcessing(); void setEnableImageProcessing(int enableImageProcessing); int getDensity(); void setDensity(int density); int getDepth(); void setDepth(int depth); String getColorspace(); void setColorspace(String colorspace); String getFilter(); void setFilter(String filter); int getResize(); void setResize(int resize); String getImageMagickPath(); void setImageMagickPath(String imageMagickPath); boolean getApplyRotation(); void setApplyRotation(boolean applyRotation); Map<String, String> getOtherTesseractConfig(); void addOtherTesseractConfig(String key, String value);  }### Answer:
@Test(expected=IllegalArgumentException.class) public void testValidateFilter() { TesseractOCRConfig config = new TesseractOCRConfig(); config.setFilter("Triangle"); config.setFilter("box"); assertTrue("Couldn't set valid values", true); config.setFilter("abc"); }