* variety of sequences of the {@link Iterator#next}, {@link Iterator#hasNext} and {@link
 * Iterator#remove} operations. This utility takes the brute-force approach of trying <i>all</i>
 * possible sequences of these operations, up to a given number of steps. So, if the caller
 * specifies to use <i>n</i> steps, a total of <i>3^n</i> tests are actually performed.
 *

    if (testDir != null) {
      return testDir;
    }

    URL testFileUrl = IoTestCase.class.getResource("testdata/i18n.txt");
    if (testFileUrl == null) {
      throw new RuntimeException("unable to locate testdata directory");
    }

    if (testFileUrl.getProtocol().equals("file")) {
      try {
        File testFile = new File(testFileUrl.toURI());
        testDir = testFile.getParentFile(); // the testdata directory

        return new VerticalLinearTransformation(x1);
      } else {
        return withSlope((y2 - y1) / (x2 - x1));
      }
    }

    /**
     * Finish building an instance with the given slope, i.e. the rate of change of {@code y} with
     * respect to {@code x}. The slope must not be {@code NaN}. It may be infinite, in which case
     * the transformation is vertical. (If it is zero, the transformation is horizontal.)
     */

 * variety of sequences of the {@link Iterator#next}, {@link Iterator#hasNext} and {@link
 * Iterator#remove} operations. This utility takes the brute-force approach of trying <i>all</i>
 * possible sequences of these operations, up to a given number of steps. So, if the caller
 * specifies to use <i>n</i> steps, a total of <i>3^n</i> tests are actually performed.
 *

    if (testDir != null) {
      return testDir;
    }

    URL testFileUrl = IoTestCase.class.getResource("testdata/i18n.txt");
    if (testFileUrl == null) {
      throw new RuntimeException("unable to locate testdata directory");
    }

    if (testFileUrl.getProtocol().equals("file")) {
      try {
        File testFile = new File(testFileUrl.toURI());
        testDir = testFile.getParentFile(); // the testdata directory