Re: Need help designing some JUnit tests
Rhino wrote:
Actually, my getLocales() method is really just a convenience method that
massages the results of Locale.getAvailableLocales() itself.
Just to be sure I'm using the term "convenience method" correctly, I'm
referring to a method I write that uses existing Java API methods but
that combines several lines of code into one or two. For example, since I
Yep.
prefer my Locales list to be in alphabetical order, I've written this:
public Map<String, String> getLocales() {
Locale[] listOfLocales = Locale.getAvailableLocales();
Map<String, String> locales = new TreeMap<String, String>();
for (Locale singleLocale : listOfLocales) {
locales.put(singleLocale.toString(), singleLocale.getDisplayName
(locale));
Umm, what is 'locale' in this line? I mean, it's obvious that it's a
'Locale', but what is it?
}
return locales;
}
Your 'listOfLocales' variable is, perhaps, not necessary.
That idiom also works if you want to retrieve the Locales themselves based on
name:
Map <String, Locale> locales = new TreeMap <String, Locale> ();
for( Locale loc : Locale.getAvailableLocales() )
{
locales.put( loc.getDisplayName(locale), loc );
}
or something like.
As such, I don't know how to do a JUnit test on it, specifically how to
generate an expected result that can be compared to my actual result. It
seems self-evident that I have to get my expected result in a different
way than I get the actual result, otherwise, I'm not proving anything.
Unit tests cannot do everything that the class under test does, otherwise the
unit test class would be the class under test. What unit tests do is test the
"happy path" and various corner cases to provide a high level of certainty
that the tested class will correctly handle the infinite variety of stuff
thrown at it in production. In other words, a unit test is really a sanity
check that takes care of the most likely issues. If a unit test could prevent
all possible errors, we'd never need logging.
For your case, you might test that the 'Map' has the same number of entries as
'getLocales()' has elements and that it correctly returns the right values for
some representative keys.
....
Or is it the case that such a method CAN'T have its accuracy tested in
this way and no such attempt should be made? Is it enough to prove that
the method executes without throwing an exception?
You should go farther than that.
--------------------------------
Scenario 3 - getInstance()
Given a hypothetical class named Fuzz where the constructors and
getInstance() methods are:
private Fuzz() {
// do something
}
private Fuzz(Locale locale) {
// do something
// initialize instance variable for locale
}
public getInstance() {
Lew wrote:
Where is your return value?
This won't even compile.
Rhino wrote:
Sorry, I just hacked that together to save a minute. I probably should
have copied in a compiled example....
Oopsie. (Giggle)
Would the following be adequate as JUnit tests for the getInstance()
methods?
public void testGetInstance() {
Fuzz fuzz = Fuzz.getInstance();
if (!fuzz instanceof Fuzz) fail("Failed to instantiate Fuzz");
}
...
So, if the constructor doesn't
throw any exceptions and is public, you say that I should test that "the
returned values exists and is not null".
Non-nullity of the return value should be handled by an 'assert' in the
factory method, and therefore not necessary to test in the unit test.
Existence is already guaranteed by the successful return of the factory method.
What's my best way of doing that? Am I right in assuming that a simple
if (Foo != null)
Ummm, 'Foo' is a class, right? It better be, and therefore that line will not
compile.
will cover both of those?
How about 'assertNotNull( fuzz );'?
--
Lew