The test class `KeywordFieldMapperTests` contains a switch statement with a branch that will never execute. The test uses a `between(x, y)` switch expression, but the `4` case is outside the randomised range. We need to fix this before #88739 can be merged. By "fix", I mean either remove the spurious case, or if we actually want it then extend the randomized range.
server/src/test/java/org/elasticsearch/index/mapper/KeywordFieldMapperTests.java
public void testDimensionInRoutingPath() throws IOException {
        MapperService mapper = createMapperService(fieldMapping(b -> b.field("type", "keyword").field("time_series_dimension", true)));
        IndexSettings settings = createIndexSettings(
            Version.CURRENT,
            Settings.builder()
                .put(IndexSettings.MODE.getKey(), "time_series")
                .put(IndexMetadata.INDEX_ROUTING_PATH.getKey(), "field")
                .put(IndexSettings.TIME_SERIES_START_TIME.getKey(), "2021-04-28T00:00:00Z")
                .put(IndexSettings.TIME_SERIES_END_TIME.getKey(), "2021-04-29T00:00:00Z")
                .build()
        );
        mapper.documentMapper().validate(settings, false);  
    }
    public void testKeywordFieldUtf8LongerThan32766() throws Exception {
        DocumentMapper mapper = createDocumentMapper(fieldMapping(b -> b.field("type", "keyword")));
        StringBuilder stringBuilder = new StringBuilder(32768);
        for (int i = 0; i < 32768; i++) {
            stringBuilder.append("a");
        }
        MapperParsingException e = expectThrows(
            MapperParsingException.class,
            () -> mapper.parse(source(b -> b.field("field", stringBuilder.toString())))
        );
        assertThat(e.getCause().getMessage(), containsString("UTF8 encoding is longer than the max length"));
    }
    @Override
    protected SyntheticSourceSupport syntheticSourceSupport() {
        return new KeywordSyntheticSourceSupport();
    }
    static class KeywordSyntheticSourceSupport implements SyntheticSourceSupport {