assertNull(range.getRecommendedVersion(), CHECK_VERSION_RECOMMENDATION);
        assertFalse(range.isSelectedVersionKnown(artifact), CHECK_SELECTED_VERSION_KNOWN);
        assertNull(range.getSelectedVersion(artifact), CHECK_SELECTED_VERSION);

        range = VersionRange.createFromVersionSpec("1.0");
        assertEquals("1.0", range.getRecommendedVersion().toString(), CHECK_VERSION_RECOMMENDATION);

 * @since 4.0.0
 */
@Experimental
public interface VersionConstraint {
    /**
     * Returns the range of this constraint, or {@code null} if none.
     * <p>
     * Note: only one, this method or {@link #getRecommendedVersion()} method must return non-{@code null} value.
     */
    @Nullable
    VersionRange getVersionRange();

    /**
     * Returns the recommended version of this constraint, or {@code null} if none.
     * <p>

        VersionConstraint c = versionParser.parseVersionConstraint("1.0");
        assertEquals("1.0", c.getRecommendedVersion().toString());
        assertTrue(c.contains(versionParser.parseVersion("1.0")));

        c = versionParser.parseVersionConstraint("[1.0]");
        assertNull(c.getRecommendedVersion());
        assertTrue(c.contains(versionParser.parseVersion("1.0")));

                } else if (version == null
                        && restriction.getRecommendedVersion() != null
                        && r.containsVersion(restriction.getRecommendedVersion())) {
                    // use this if we can, but prefer the original if possible
                    version = restriction.getRecommendedVersion();
                }
            }
        }

        selectVersionFromNewRangeIfAvailable();
    }

    private void selectVersionFromNewRangeIfAvailable() {
        if ((versionRange != null) && (versionRange.getRecommendedVersion() != null)) {
            selectVersion(versionRange.getRecommendedVersion().toString());
        } else {
            version = null;
            baseVersion = null;
        }
    }

    @Override

                return null;
            }
            return new DefaultVersionRange(versionScheme, delegate.getRange());
        }

        @Override
        public Version getRecommendedVersion() {
            if (delegate.getVersion() == null) {
                return null;
            }
            return new DefaultVersion(versionScheme, delegate.getVersion());
        }

        @Override