FizzBuzz.java

package net.clarenceho.test;

public class FizzBuzz {

    public static String doFizzBuzz1(int i) {
        StringBuilder sb = new StringBuilder();
        if (i % 3 == 0) {
            sb.append("Fizz");
        }
        if (i % 5 == 0) {
            sb.append("Buzz");
        }
        if (sb.length() == 0) {
            sb.append(i);
        }
        
        return sb.toString();
    }
    
    public static String doFizzBuzz2(int i) {
        if (i % 3 == 0) {
            if (i % 5 == 0) {
                return "FizzBuzz";
            } else {
                return "Fizz";
            }
        } else if (i % 5 == 0) {
            return "Buzz";
        }
        return String.valueOf(i);
    }
    
    public static String doFizzBuzz3(int i) {
        if (i % 15 == 0) {
            return "FizzBuzz";
        } else if (i % 5 == 0) {
            return "Buzz";
        } else if (i % 3 == 0) {
            return "Fizz";
        }
        return String.valueOf(i);
    }    
}

TestFizzBuzz.java

package net.clarenceho.test;

import java.util.ArrayList;
import java.util.List;
import java.util.function.Function;
import java.util.stream.IntStream;
import static org.junit.Assert.*;

import org.junit.Before;
import org.junit.FixMethodOrder;
import org.junit.Test;
import org.junit.runners.MethodSorters;

@FixMethodOrder(MethodSorters.NAME_ASCENDING)
public class TestFizzBuzz {
    
    String expected[] = {
        "FizzBuzz", "1", "2", "Fizz", "4", "Buzz",
        "Fizz", "7", "8", "Fizz", "Buzz",
        "11", "Fizz", "13", "14", "FizzBuzz",
        "16", "17", "Fizz", "19", "Buzz",
        "Fizz", "22", "23", "Fizz", "Buzz",
        "26", "Fizz", "28", "29", "FizzBuzz",
    };
    
    // list of FizzBuzz methods to test
    List<Function<Integer, String>> methods = new ArrayList<>();
    
    @Before
    public void setup() {
        methods.add(FizzBuzz::doFizzBuzz1);
        methods.add(FizzBuzz::doFizzBuzz2);
        methods.add(FizzBuzz::doFizzBuzz3);
    }
    
    @Test
    public void doSample() {
        for (Function<Integer, String> m: methods) {
            for (int i = 0; i < expected.length; i++) {
                assertEquals(expected[i], m.apply(i));
            }
        }
    }
    
    @Test
    public void testMaxRange() {
        for (Function<Integer, String> m: methods) {
            assertTrue(autoTest(m, Integer.MIN_VALUE, Integer.MAX_VALUE));
        }
    }

    @Test
    public void timeAll() {
        for (Function<Integer, String> m: methods) {
            long start = System.nanoTime();
            autoTest(m, Integer.MIN_VALUE, Integer.MAX_VALUE);
            long end = System.nanoTime();
            System.err.println("Time taken to run " + m.toString() + " is " + ((end - start) / 1000000000.0) +"s");
        }
    }

    private boolean autoTest(Function<Integer, String> opr, int start, int end) {
        return IntStream
            .range(start, end)
            .parallel()
            .map(i -> {
                String r = opr.apply(i);
                if (i % 15 == 0 && "FizzBuzz".equals(r)) {
                    return 0;
                } else if (i % 3 == 0 && "Fizz".equals(r)) {
                    return 0;
                } else if (i % 5 == 0 && "Buzz".equals(r)) {
                    return 0;
                } else if (String.valueOf(i).equals(r)) {
                    return 0;
                }
                return 1;
            })
            .filter(i -> i != 0)
            .findFirst()
            .isPresent() == false;
    }

}