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4d47's solution

to Two Fer in the Java Track

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Instructions
Test suite
Solution

Two-fer or 2-fer is short for two for one. One for you and one for me.

"One for X, one for me."

When X is a name or "you".

If the given name is "Alice", the result should be "One for Alice, one for me." If no name is given, the result should be "One for you, one for me."

Java Tips

Before you start, make sure you understand how to write code that can pass the test cases. For more context, check out this tutorial.

Most Java exercises include multiple test cases. These cases are structured to support a useful process known as test-driven development (TDD). TDD involves repeating a structured cycle that helps programmers build complex functionality piece by piece rather than all at once. That cycle can be described as follows:

  1. Add a test that describes one piece of desired functionality your code is currently missing.
  2. Run the tests to verify that this newly-added test fails.
  3. Update your existing code until:
    • All the old tests continue to pass;
    • The new test also passes.
  4. Clean up your code, making sure that all tests continue to pass. This typically involves renaming variables, removing duplicated chunks of logic, removing leftover logging, etc.
  5. Return to step 1 until all desired functionality has been built!

The test files in this track contain all the tests your solution should pass to be considered valid. That doesn't immediately seem to be compatible with the cycle described above, in which tests are written one by one. However, the tool that we use to write our tests, JUnit, provides an @Ignore annotation that can be used to temporarily skip an already-written test. Using this annotation, we make sure that the test files we deliver to you satisfy the following rules:

  • The first test in any test file is not skipped by default.
  • All but the first test in any test file are skipped by default.

This allows you to simulate the TDD cycle by following these slightly-modified steps:

  1. Run the tests to verify that at most one test currently fails.
  2. Update your existing code until all the non-skipped tests pass.
  3. Clean up your code, making sure that all non-skipped tests continue to pass.
  4. Remove the topmost @Ignore annotation in the test file.
  5. Return to step 1 until no tests are skipped and all tests pass!

Running the tests

You can run all the tests for an exercise by entering

$ gradle test

in your terminal.

Source

https://en.wikipedia.org/wiki/Two-fer

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

TwoferTest.java

import org.junit.Before;
import org.junit.Ignore;
import org.junit.Test;

import static org.junit.Assert.assertEquals;

public class TwoferTest {

    private Twofer twofer;

    @Before
    public void setup() {
        twofer = new Twofer();
    }

    @Test
    public void noNameGiven() {
        String input = null;
        String expected = "One for you, one for me.";

        assertEquals(expected, twofer.twofer(input));
    }

    @Ignore("Remove to run test")
    @Test
    public void aNameGiven() {
        String input = "Alice";
        String expected = "One for Alice, one for me.";

        assertEquals(expected, twofer.twofer(input));
    }

    @Ignore("Remove to run test")
    @Test
    public void anotherNameGiven() {
        String input = "Bob";
        String expected = "One for Bob, one for me.";

        assertEquals(expected, twofer.twofer(input));
    }
}
class Twofer {
    String twofer(final String name) {
        return String.format("One for %s, one for me.", name == null ? "you" : name);
    }
}

What can you learn from this solution?

A huge amount can be learnt from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that I could read more about to develop my understanding?