But at some point, there was no other option than creating something that provided all these features, taking the best ideas from previous tools, and combining them in the best way possible, using language features that weren't even available before (Python 3.6+ type hints).

## Previous tools

import static com.google.common.collect.testing.features.CollectionFeature.FAILS_FAST_ON_CONCURRENT_MODIFICATION;
import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_REMOVE;
import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;

package com.google.common.collect.testing.google;

import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_VALUES;
import static com.google.common.collect.testing.features.MapFeature.SUPPORTS_PUT;

 */

package com.google.common.collect.testing.testers;

import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static java.util.Arrays.asList;

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.testing.features.CollectionSize;
import org.junit.Ignore;

/**
 * A generic JUnit test which tests {@code toArray()} operations on a list. Can't be invoked

import static com.google.common.collect.testing.features.CollectionSize.ONE;
import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEYS;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_VALUES;

import static com.google.common.collect.testing.features.CollectionFeature.ALLOWS_NULL_QUERIES;
import static com.google.common.collect.testing.features.CollectionFeature.ALLOWS_NULL_VALUES;
import static com.google.common.collect.testing.features.CollectionFeature.FAILS_FAST_ON_CONCURRENT_MODIFICATION;
import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_REMOVE;

          parentBuilder) {
    Set<Feature<?>> features = computeMultimapAsMapGetFeatures(parentBuilder.getFeatures());
    if (Collections.disjoint(features, EnumSet.allOf(CollectionSize.class))) {
      return new TestSuite();
    } else {
      return SetTestSuiteBuilder.using(
              new MultimapAsMapGetGenerator<K, V>(parentBuilder.getSubjectGenerator()))
          .withFeatures(features)

import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEYS;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEY_QUERIES;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_VALUES;

    public static final String FEATURE_SECURE_PROCESSING = "http://javax.xml.XMLConstants/feature/secure-processing";

    public static final String FEATURE_EXTERNAL_GENERAL_ENTITIES = "http://xml.org/sax/features/external-general-entities";

    public static final String FEATURE_EXTERNAL_PARAMETER_ENTITIES = "http://xml.org/sax/features/external-parameter-entities";

    private Constants() {
    }

import static com.google.common.collect.testing.features.CollectionFeature.ALLOWS_NULL_VALUES;
import static com.google.common.collect.testing.features.CollectionFeature.REJECTS_DUPLICATES_AT_CREATION;
import static com.google.common.collect.testing.features.CollectionSize.ONE;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;