### Question:
EquatableValueSet implements ValueSet { @Override public Object getSingleValue() { if (!isSingleValue()) { throw new IllegalStateException("EquatableValueSet does not have just a single value"); } return entries.iterator().next().getValue(); } @JsonCreator  EquatableValueSet(
            @JsonProperty("type") Type type,
            @JsonProperty("inclusive") boolean inclusive,
            @JsonProperty("entries") Set<ValueEntry> entries); @JsonProperty @Override Type getType(); @JsonProperty boolean inclusive(); @JsonProperty Set<ValueEntry> getEntries(); Collection<Object> getValues(); int getValuesCount(); @Override boolean isNone(); @Override boolean isAll(); @Override boolean isSingleValue(); @Override Object getSingleValue(); @Override boolean isDiscreteSet(); @Override List<Object> getDiscreteSet(); @Override boolean containsValue(Object value); @Override DiscreteValues getDiscreteValues(); @Override ValuesProcessor getValuesProcessor(); @Override EquatableValueSet intersect(ValueSet other); @Override boolean overlaps(ValueSet other); @Override EquatableValueSet union(ValueSet other); @Override EquatableValueSet complement(); @Override String toString(); @Override String toString(ConnectorSession session); @Override int hashCode(); @Override boolean equals(Object obj);  }### Answer:
@Test public void testGetSingleValue() { assertEquals(EquatableValueSet.of(ID, 0L).getSingleValue(), 0L); try { EquatableValueSet.all(ID).getSingleValue(); fail(); } catch (IllegalStateException ignored) { } }