gson-comments/gson/src/test/java/com/google/gson/functional/ReusedTypeVariablesFullyResolveTest.java

package com.google.gson.functional;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import org.junit.Before;
import org.junit.Test;

import java.util.Collection;
import java.util.Iterator;
import java.util.Set;

import static org.junit.Assert.*;

/**
 * This test covers the scenario described in #1390 where a type variable needs to be used
 * by a type definition multiple times.  Both type variable references should resolve to the
 * same underlying concrete type.
 */
public class ReusedTypeVariablesFullyResolveTest {

    private Gson gson;

    @Before
    public void setUp() {
        gson = new GsonBuilder().create();
    }

    @SuppressWarnings("ConstantConditions") // The instances were being unmarshaled as Strings instead of TestEnums
    @Test
    public void testGenericsPreservation() {
        TestEnumSetCollection withSet = gson.fromJson("{\"collection\":[\"ONE\",\"THREE\"]}", TestEnumSetCollection.class);
        Iterator<TestEnum> iterator = withSet.collection.iterator();
        assertNotNull(withSet);
        assertNotNull(withSet.collection);
        assertEquals(2, withSet.collection.size());
        TestEnum first = iterator.next();
        TestEnum second = iterator.next();

        assertTrue(first instanceof TestEnum);
        assertTrue(second instanceof TestEnum);
    }

    enum TestEnum { ONE, TWO, THREE }

    private static class TestEnumSetCollection extends SetCollection<TestEnum> {}

    private static class SetCollection<T> extends BaseCollection<T, Set<T>> {}

    private static class BaseCollection<U, C extends Collection<U>>
    {
        public C collection;
    }

}