@Test
public void testUpdate() {

    Map<Integer, double[]> data = new HashMap<>();
    data.put(0, new double[]{-1.0915526, 1.81983527, -0.91409478, 0.70890712, -24.55724107});
    data.put(1, new double[]{-0.61072904, 0.37545517, 0.21705352, 0.09516495, -26.57226867});
    data.put(2, new double[]{0.05485406, 0.88219898, -0.80584547, 0.94668307, 61.80919728});
    data.put(3, new double[]{-0.24835094, -0.34000053, -1.69984651, -1.45902635, -161.65525991});
    data.put(4, new double[]{0.63675392, 0.31675535, 0.38837437, -1.1221971, -14.46432611});
    data.put(5, new double[]{0.14194017, 2.18158997, -0.28397346, -0.62090588, -3.2122197});
    data.put(6, new double[]{-0.53487507, 1.4454797, 0.21570443, -0.54161422, -46.5469012});
    data.put(7, new double[]{-1.58812173, -0.73216803, -2.15670676, -1.03195988, -247.23559889});
    data.put(8, new double[]{0.20702671, 0.92864654, 0.32721202, -0.09047503, 31.61484949});
    data.put(9, new double[]{-0.37890345, -0.04846179, -0.84122753, -1.14667474, -124.92598583});
    LinearRegressionSGDTrainer<?> trainer = new LinearRegressionSGDTrainer<>(new UpdatesStrategy<>(
        new RPropUpdateCalculator(),
        RPropParameterUpdate.SUM_LOCAL,
        RPropParameterUpdate.AVG
    ), 1800, 10, 10, 123L);
    LinearRegressionModel originalMdl = trainer.withSeed(0).fit(
        data, parts,
        new DoubleArrayVectorizer<Integer>().labeled(Vectorizer.LabelCoordinate.LAST)
    );
    LinearRegressionModel updatedOnSameDS = trainer.withSeed(0).update(
        originalMdl,
        data,
        parts,
        new DoubleArrayVectorizer<Integer>().labeled(Vectorizer.LabelCoordinate.LAST)
    );
    LinearRegressionModel updatedOnEmptyDS = trainer.withSeed(0).update(
        originalMdl,
        new HashMap<>(),
        parts,
        new DoubleArrayVectorizer<Integer>().labeled(Vectorizer.LabelCoordinate.LAST)
    );
    assertArrayEquals(
        originalMdl.getWeights().getStorage().data(),
        updatedOnSameDS.getWeights().getStorage().data(),
        1.0
    );
    assertEquals(originalMdl.getIntercept(), updatedOnSameDS.getIntercept(), 1.0);
    assertArrayEquals(
        originalMdl.getWeights().getStorage().data(),
        updatedOnEmptyDS.getWeights().getStorage().data(),
        1e-1
    );
    assertEquals(originalMdl.getIntercept(), updatedOnEmptyDS.getIntercept(), 1e-1);
}