Re: Tests for several classes implementing a generic interface

From:
markspace <nospam@nowhere.com>
Newsgroups:
comp.lang.java.help
Date:
Thu, 06 May 2010 10:01:52 -0700
Message-ID:
<hrusm3$u8m$1@news.eternal-september.org>
kofa wrote:

Then, I'd like to have a test where I only need to change the line
that instantiates the object under test. I've come up with:
public class ThingTest<T> {


I haven't thought this through completely, but I think the correct way
to do this is to create this class with a constructor that takes a type
token. Example:

   public class ThingTest<T> {
     private Class<T> type;
     public ThingTest( Class<T> type ) {
       this.type = type;
     }
   ....
}

Now you have some means of actually testing the type.

  private Something<T> underTest = (Something<T>) new IntegerThing();


     private Something<?> underTest = new IntegerThing();

  @Test
  public void test() {
    T thingA = underTest.createThing();


       T thingA = type.cast( underTest.createThing() );
       ...etc....

    T thingB = underTest.createThing();
    underTest.doSomething(thingA, thingB);
    Set<T> result = underTest.getThings();
    // assert whatever...
  }
}


Furthermore, you might be able to type check the "underTest" object too.

   public class ThingTest<T> {
     private Class<T> type;
     private Something<T> underTest;
     public ThingTest( Class<T> type, Something<T> underTest ) {
       this.type = type;
       this.underTest = underTest;
     }
   ....
}

Now you invoke your test object like this:

  ThingTest<Integer> testHarness = new ThingTest<Integer>( Integer.class,
                                                  new IntegerThing() );

That combo of parameters is the only ones the compiler will allow.

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