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/*

* Reference Huffman coding

* Copyright (c) Project Nayuki

*

* https://www.nayuki.io/page/reference-huffman-coding

* https://github.com/nayuki/Reference-Huffman-coding

*/

import java.io.EOFException;

import java.io.IOException;

import java.util.Random;

import org.junit.Assert;

import org.junit.Test;

/**

* Tests the compression and decompression of a complete Huffman coding application, using the JUnit test framework.

*/

public abstract class HuffmanCodingTest {

/* Test cases */

@Test public void testEmpty() {

test(new byte[0]);

}

@Test public void testOneSymbol() {

test(new byte[10]);

}

@Test public void testSimple() {

test(new byte[]{0, 3, 1, 2});

}

@Test public void testEveryByteValue() {

byte[] b = new byte[256];

for (int i = 0; i < b.length; i++)

b[i] = (byte)i;

test(b);

}

@Test public void testFibonacciFrequencies() {

byte[] b = new byte[87];

int i = 0;

for (int j = 0; j < 1; j++, i++) b[i] = 0;

for (int j = 0; j < 2; j++, i++) b[i] = 1;

for (int j = 0; j < 3; j++, i++) b[i] = 2;

for (int j = 0; j < 5; j++, i++) b[i] = 3;

for (int j = 0; j < 8; j++, i++) b[i] = 4;

for (int j = 0; j < 13; j++, i++) b[i] = 5;

for (int j = 0; j < 21; j++, i++) b[i] = 6;

for (int j = 0; j < 34; j++, i++) b[i] = 7;

test(b);

}

@Test public void testRandomShort() {

for (int i = 0; i < 100; i++) {

byte[] b = new byte[random.nextInt(1000)];

random.nextBytes(b);

test(b);

}

}

@Test public void testRandomLong() {

for (int i = 0; i < 3; i++) {

byte[] b = new byte[random.nextInt(1000000)];

random.nextBytes(b);

test(b);

}

}

/* Utilities */

// Tests that the given byte array can be compressed and decompressed to the same data, and not throw any exceptions.

private void test(byte[] b) {

try {

byte[] compressed = compress(b);

byte[] decompressed = decompress(compressed);

Assert.assertArrayEquals(b, decompressed);

} catch (EOFException e) {

Assert.fail("Unexpected EOF");

} catch (IOException e) {

throw new AssertionError(e);

}

}

private static Random random = new Random();

/* Abstract methods */

// Compression method that needs to be supplied by a subclass.

protected abstract byte[] compress(byte[] b) throws IOException;

// Decompression method that needs to be supplied by a subclass.

protected abstract byte[] decompress(byte[] b) throws IOException;

}