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
{
            Exception e = expectThrows(MapperParsingException.class, () -> createDocumentMapper(fieldMapping(b -> {
                minimalMapping(b);
                b.field("time_series_dimension", true).field("index", false).field("doc_values", true);
            })));
            assertThat(
                e.getCause().getMessage(),
                containsString("Field [time_series_dimension] requires that [index] and [doc_values] are true")
            );
        }
    }
    public void testDimensionMultiValuedField() throws IOException {
        XContentBuilder mapping = fieldMapping(b -> {
            minimalMapping(b);
            b.field("time_series_dimension", true);
        });
        DocumentMapper mapper = randomBoolean() ? createDocumentMapper(mapping) : createTimeSeriesModeDocumentMapper(mapping);
        Exception e = expectThrows(MapperParsingException.class, () -> mapper.parse(source(b -> b.array("field", "1234", "45678"))));
        assertThat(e.getCause().getMessage(), containsString("Dimension field [field] cannot be a multi-valued field"));
    }
    public void testDimensionExtraLongKeyword() throws IOException {
        DocumentMapper mapper = createTimeSeriesModeDocumentMapper(fieldMapping(b -> {
            minimalMapping(b);
            b.field("time_series_dimension", true);
        }));
        Exception e = expectThrows(
            MapperParsingException.class,
            () -> mapper.parse(source(b -> b.field("field", randomAlphaOfLengthBetween(1025, 2048))))
        );
        assertThat(e.getCause().getMessage(), containsString("Dimension fields must be less than [1024] bytes but was"));