@Override
    public void add(IndexSpec indexSpec) {
        checkIndexSpec(indexSpec);
        var indexName = indexSpec.getName();
        var existingSpec = indexSpecs.putIfAbsent(indexName, indexSpec);
        if (existingSpec != null) {
            throw new IllegalArgumentException(
                "IndexSpec with name " + indexName + " already exists");
        }
    }
@Test
    void add() {
        var specs = new DefaultIndexSpecs();
        specs.add(primaryKeyIndexSpec(FakeExtension.class));
        assertThat(specs.contains(PrimaryKeySpecUtils.PRIMARY_INDEX_NAME)).isTrue();
    }