JUnit Cookbook

Kent Beck, Erich Gamma

Simple Test Case

単純なテストケース

The simplest way is as an expression in a debugger. You can change debug expressions without recompiling, and you can wait to decide what to write until you have seen the running objects. You can also write test expressions as statements which print to the standard output stream. Both styles of tests are limited because they require human judgment to analyze their results. Also, they don't compose nicely- you can only execute one debug expression at a time and a program with too many print statements causes the dreaded "Scroll Blindness".

JUnit tests do not require human judgment to interpret, and it is easy to run many of them at the same time. When you need to test something, here is what you do:

1. Annotate a method with @org.junit.Test
   メソッドに@org.junit.Testの注釈(アノテーション)を加えます
2. When you want to check a value, import org.junit.Assert.* statically, call assertTrue() and pass a boolean that is true if the test succeeds
   値をチェックしたい時は、org.junit.Assert.*を静的に(static)インポートし、assertTrue()を呼び出し、テストが成功した時はtrueとなる真偽値を渡します

@Test public void simpleAdd() {
    Money m12CHF= new Money(12, "CHF"); 
    Money m14CHF= new Money(14, "CHF"); 
    Money expected= new Money(26, "CHF"); 
    Money result= m12CHF.add(m14CHF); 
    assertTrue(expected.equals(result));
}

Fixture

付属品

Tests need to run against the background of a known set of objects. This set of objects is called a test fixture. When you are writing tests you will often find that you spend more time writing the code to set up the fixture than you do in actually testing values.

To some extent, you can make writing the fixture code easier by paying careful attention to the constructors you write. However, a much bigger savings comes from sharing fixture code. Often, you will be able to use the same fixture for several different tests. Each case will send slightly different messages or parameters to the fixture and will check for different results.

When you have a common fixture, here is what you do:

1. Add a field for each part of the fixture
   付属品の各部分にフィールドを加えます
2. Annotate a method with @org.junit.Before and initialize the variables in that method
   メソッドに@org.junit.Beforeの注釈(アノテーション)を加え、メソッド内で値を初期化します
3. Annotate a method with @org.junit.After to release any permanent resources you allocated in setUp
   セットアップで割り当てたいくつかの永続的なリソースを解放するために、メソッドに@org.junit.Afterの注釈(アノテーション)を加えます

public class MoneyTest { 
    private Money f12CHF; 
    private Money f14CHF; 
    private Money f28USD; 
    
    @Before public void setUp() { 
        f12CHF= new Money(12, "CHF"); 
        f14CHF= new Money(14, "CHF"); 
        f28USD= new Money(28, "USD"); 
    }
}

TestRunner

テストランナー

Once you have tests, you'll want to run them. JUnit provides tools to define the suite to be run and to display its results. To run tests and see the results on the console, run:

org.junit.runner.TextListener.run(TestClass1.class, ...); 

public static junit.framework.Test suite() { 
    return new JUnit4TestAdapter(Example.class); 
}

Expected Exceptions

期待された例外

Verifying that code completes normally is only part of programming. Making sure the code behaves as expected in exceptional situations is part of the craft of programming too. For example:

new ArrayList<Object>().get(0); 

@Test(expected= IndexOutOfBoundsException.class) public void empty() { 
    new ArrayList<Object>().get(0); 
}