Add trivial dependencies tests for the network stack

/*

 * Copyright (C) 2020 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package android.net;

import static org.junit.Assert.assertArrayEquals;

import static org.junit.Assert.assertEquals;

import static org.junit.Assert.assertFalse;

import androidx.test.filters.SmallTest;

import androidx.test.runner.AndroidJUnit4;

import org.junit.Test;

import org.junit.runner.RunWith;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.concurrent.TimeUnit;

/**

 * A simple class that tests dependencies to java standard tools from the

 * Network stack. These tests are not meant to be comprehensive tests of

 * the relevant APIs : such tests belong in the relevant test suite for

 * these dependencies. Instead, this just makes sure coverage is present

 * by calling the methods in the exact way (or a representative way of how)

 * they are called in the network stack.

 */

@RunWith(AndroidJUnit4.class)

@SmallTest

public class DependenciesTest {

    // Used to in ipmemorystore's RegularMaintenanceJobService to convert

    // 24 hours into seconds

    @Test

    public void testTimeUnit() {

        final int hours = 24;

        final long inSeconds = TimeUnit.HOURS.toMillis(hours);

        assertEquals(inSeconds, hours * 60 * 60 * 1000);

    }

    private byte[] makeTrivialArray(final int size) {

        final byte[] src = new byte[size];

        for (int i = 0; i < size; ++i) {

            src[i] = (byte) i;

        }

        return src;

    }

    // Used in ApfFilter to find an IP address from a byte array

    @Test

    public void testArrays() {

        final int size = 128;

        final byte[] src = makeTrivialArray(size);

        // Test copy

        final int copySize = 16;

        final int offset = 24;

        final byte[] expected = new byte[copySize];

        for (int i = 0; i < copySize; ++i) {

            expected[i] = (byte) (offset + i);

        }

        final byte[] copy = Arrays.copyOfRange(src, offset, offset + copySize);

        assertArrayEquals(expected, copy);

        assertArrayEquals(new byte[0], Arrays.copyOfRange(src, size, size));

    }

    // Used mainly in the Dhcp code

    @Test

    public void testCopyOf() {

        final byte[] src = makeTrivialArray(128);

        final byte[] copy = Arrays.copyOf(src, src.length);

        assertArrayEquals(src, copy);

        assertFalse(src == copy);

        assertArrayEquals(new byte[0], Arrays.copyOf(src, 0));

        final int excess = 16;

        final byte[] biggerCopy = Arrays.copyOf(src, src.length + excess);

        for (int i = src.length; i < src.length + excess; ++i) {

            assertEquals(0, biggerCopy[i]);

        }

        for (int i = src.length - 1; i >= 0; --i) {

            assertEquals(src[i], biggerCopy[i]);

        }

    }

    // Used mainly in DnsUtils but also various other places

    @Test

    public void testAsList() {

        final int size = 24;

        final Object[] src = new Object[size];

        final ArrayList<Object> expected = new ArrayList<>(size);

        for (int i = 0; i < size; ++i) {

            final Object o = new Object();

            src[i] = o;

            expected.add(o);

        }

        assertEquals(expected, Arrays.asList(src));

    }

}