The following issues were found

src/test/java/io/reactivex/rxjava3/tck/ConcatWithCompletableTckTest.java
1 issues
Avoid unused imports such as 'io.reactivex.rxjava3.core'
Design

Line: 19 

              import org.reactivestreams.Publisher;
import org.testng.annotations.Test;

import io.reactivex.rxjava3.core.*;

@Test
public class ConcatWithCompletableTckTest extends BaseTck<Integer> {

    @Override

Reported by PMD.

src/test/java/io/reactivex/rxjava3/tck/ConcatMapSingleTckTest.java
1 issues
Avoid unused imports such as 'io.reactivex.rxjava3.core'
Design

Line: 19 

              import org.reactivestreams.Publisher;
import org.testng.annotations.Test;

import io.reactivex.rxjava3.core.*;
import io.reactivex.rxjava3.functions.Function;

@Test
public class ConcatMapSingleTckTest extends BaseTck<Integer> {

Reported by PMD.

src/test/java/io/reactivex/rxjava3/tck/ConcatMapMaybeTckTest.java
1 issues
Avoid unused imports such as 'io.reactivex.rxjava3.core'
Design

Line: 19 

              import org.reactivestreams.Publisher;
import org.testng.annotations.Test;

import io.reactivex.rxjava3.core.*;
import io.reactivex.rxjava3.functions.Function;

@Test
public class ConcatMapMaybeTckTest extends BaseTck<Integer> {

Reported by PMD.

src/test/java/io/reactivex/rxjava3/tck/CompletableAndThenPublisherTckTest.java
1 issues
Avoid unused imports such as 'io.reactivex.rxjava3.core'
Design

Line: 19 

              import org.reactivestreams.Publisher;
import org.testng.annotations.Test;

import io.reactivex.rxjava3.core.*;

@Test
public class CompletableAndThenPublisherTckTest extends BaseTck<Integer> {

    @Override

Reported by PMD.

src/test/java/io/reactivex/rxjava3/tck/CacheTckTest.java
1 issues
Potential violation of Law of Demeter (method chain calls)
Design

Line: 27 

                  @Override
    public Publisher<Long> createPublisher(long elements) {
        return
                Flowable.fromIterable(iterate(elements)).cache()
            ;
    }
}

Reported by PMD.

src/test/java/io/reactivex/rxjava3/tck/BufferExactSizeTckTest.java
1 issues
Potential violation of Law of Demeter (method chain calls)
Design

Line: 29 

                  @Override
    public Publisher<List<Long>> createPublisher(long elements) {
        return
            Flowable.fromIterable(iterate(elements * 2))
            .buffer(2)
        ;
    }
}

Reported by PMD.