dtonhofer

dtonhofer

Functional Programming in Java, Second Edition: Functional Programming in Java, Second Edition: JUnit code improvements for Chapter 11, pages 185 ff “Refactoring Unbounded Loops”

The same remarks apply as for “Refactoring the Traditional for Loop”

  • No init()
  • Negative tests which apply for input less than 1900, resulting in exceptions.

but we cannot implement a common interface as the method parameters change. So we wrap the new class into a class that obeys the old interface, which agains llaows us to use the same test code to test both odl and new classes.

There is also a little tweak to the semantics of the case where 1900 is already rejected - instead of returning 0, we throw. Because there basically is no result in that case.

package chapter11;

import org.junit.jupiter.api.Test;

import java.time.Year;
import java.util.function.Predicate;
import java.util.stream.IntStream;

import static org.junit.jupiter.api.Assertions.*;

public class UnboundedLoopTest {

    interface Continue {

        boolean check(int year);

    }

    interface WithContinue {

        int countFrom1900(final Continue shouldContinue);

    }

    static class LeapYearsUnboundedBefore implements WithContinue {

        public int countFrom1900(final Continue shouldContinue) {
            if (!shouldContinue.check(1900)) {
                throw new IllegalArgumentException("Cannot 'continue' right at the start!'");
            }
            int count = 0;
            for (int year = 1900; ; year += 4) {
                if (!shouldContinue.check(year)) {
                    break;
                }
                if (Year.isLeap(year)) {
                    count++;
                }
            }
            return count;
        }
    }

    // Does NOT implement WithContinue!!

    static class LeapYearsUnboundedAfter {

        public int countFrom1900(final Predicate<Integer> shouldContinue) {
            if (!shouldContinue.test(1900)) {
                throw new IllegalArgumentException("Cannot 'continue' right at the start!'");
            }
            return (int) IntStream.iterate(1900, year -> year + 4)
                    .takeWhile(shouldContinue::test)
                    .filter(Year::isLeap)
                    .count();
        }
    }

    static class LeapYearsUnboundedAfterWrapped implements WithContinue {

        private final LeapYearsUnboundedAfter ly;

        public LeapYearsUnboundedAfterWrapped(LeapYearsUnboundedAfter ly) {
            this.ly = ly;
        }

        public int countFrom1900(final Continue shouldContinue) {
            return ly.countFrom1900(year -> shouldContinue.check(year));
        }

    }

    // One should maybe have a separate method to test the throws
    
    private static void commonLeapYearsTests(final WithContinue withContinue) {
        assertAll(
                () -> assertEquals(0, withContinue.countFrom1900(year -> year <= 1900)),
                () -> assertEquals(25, withContinue.countFrom1900(year -> year <= 2000)),
                () -> assertEquals(27, withContinue.countFrom1900(year -> year <= 2010)),
                () -> assertEquals(31, withContinue.countFrom1900(year -> year <= 2025)),
                () -> assertEquals(49, withContinue.countFrom1900(year -> year <= 2100)),
                () -> assertEquals(267, withContinue.countFrom1900(year -> year <= 3000)),
                () -> assertThrows(IllegalArgumentException.class, () ->
                        withContinue.countFrom1900(year -> year < 1800)
                ),
                () -> assertThrows(IllegalArgumentException.class, () ->
                        withContinue.countFrom1900(year -> year < 1900)
                )
        );
    }

    @Test
    void leapYearCountBefore() {
        commonLeapYearsTests(new LeapYearsUnboundedBefore());
    }

    @Test
    void leapYearCountAfter() {
        commonLeapYearsTests(new LeapYearsUnboundedAfterWrapped(new LeapYearsUnboundedAfter()));
    }

}

Where Next?

Popular Pragmatic Bookshelf topics Top

jimmykiang
This test is broken right out of the box… — FAIL: TestAgent (7.82s) agent_test.go:77: Error Trace: agent_test.go:77 agent_test.go:...
New
telemachus
Python Testing With Pytest - Chapter 2, warnings for “unregistered custom marks” While running the smoke tests in Chapter 2, I get these...
New
AleksandrKudashkin
On the page xv there is an instruction to run bin/setup from the main folder. I downloaded the source code today (12/03/21) and can’t see...
New
joepstender
The generated iex result below should list products instead of product for the metadata. (page 67) iex&gt; product = %Product{} %Pento....
New
Chrichton
Dear Sophie. I tried to do the “Authorization” exercise and have two questions: When trying to plug in an email-service, I found the ...
New
jgchristopher
“The ProductLive.Index template calls a helper function, live_component/3, that in turn calls on the modal component. ” Excerpt From: Br...
New
jskubick
I’m under the impression that when the reader gets to page 136 (“View Data with the Database Inspector”), the code SHOULD be able to buil...
New
nicoatridge
Hi, I have just acquired Michael Fazio’s “Kotlin and Android Development” to learn about game programming for Android. I have a game in p...
New
jonmac
The allprojects block listed on page 245 produces the following error when syncing gradle: “org.gradle.api.GradleScriptException: A prob...
New
davetron5000
Hello faithful readers! If you have tried to follow along in the book, you are asked to start up the dev environment via dx/build and ar...
New

Other popular topics Top

AstonJ
You might be thinking we should just ask who’s not using VSCode :joy: however there are some new additions in the space that might give V...
New
AstonJ
I’ve been hearing quite a lot of comments relating to the sound of a keyboard, with one of the most desirable of these called ‘thock’, he...
New
AstonJ
Continuing the discussion from Thinking about learning Crystal, let’s discuss - I was wondering which languages don’t GC - maybe we can c...
New
AstonJ
Biggest jackpot ever apparently! :upside_down_face: I don’t (usually) gamble/play the lottery, but working on a program to predict the...
New
foxtrottwist
A few weeks ago I started using Warp a terminal written in rust. Though in it’s current state of development there are a few caveats (tab...
New
AstonJ
Was just curious to see if any were around, found this one: I got 51/100: Not sure if it was meant to buy I am sure at times the b...
New
PragmaticBookshelf
Author Spotlight: Peter Ullrich @PJUllrich Data is at the core of every business, but it is useless if nobody can access and analyze ...
New
AstonJ
This is cool! DEEPSEEK-V3 ON M4 MAC: BLAZING FAST INFERENCE ON APPLE SILICON We just witnessed something incredible: the largest open-s...
New
AstonJ
Curious what kind of results others are getting, I think actually prefer the 7B model to the 32B model, not only is it faster but the qua...
New
PragmaticBookshelf
A concise guide to MySQL 9 database administration, covering fundamental concepts, techniques, and best practices. Neil Smyth MySQL...
New

Latest in Functional Programming in Java, Second Edition

Functional Programming in Java, Second Edition Portal

Sub Categories: