### Question:
CholeskyDecompositionCommons implements Decomposition<CholeskyDecompositionResult> { @Override public CholeskyDecompositionResult apply(DoubleMatrix x) { ArgChecker.notNull(x, "x"); RealMatrix temp = CommonsMathWrapper.wrap(x); CholeskyDecomposition cholesky; try { cholesky = new CholeskyDecomposition(temp); } catch (Exception e) { throw new MathException(e.toString()); } return new CholeskyDecompositionCommonsResult(cholesky); }  @Override CholeskyDecompositionResult apply(DoubleMatrix x);  }### Answer:
@Test public void testNullObjectMatrix() { assertThatIllegalArgumentException() .isThrownBy(() -> CH.apply((DoubleMatrix) null)); }
@Test public void testRecoverOrginal() { final DecompositionResult result = CH.apply(A); assertThat(result instanceof CholeskyDecompositionResult).isTrue(); final CholeskyDecompositionResult ch = (CholeskyDecompositionResult) result; final DoubleMatrix a = (DoubleMatrix) ALGEBRA.multiply(ch.getL(), ch.getLT()); checkEquals(A, a); }