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Null Analysis and Unit Tests [message #1219196]

Mon, 02 December 2013 15:24

Philippe Marschall

Messages: 121
Registered: July 2009

Senior Member

Hi

We're evaluating the null analysis in JDT and we encountered some issues
that are annoying in unit tests. The cause is that null analysis doesn't
seem to understand that certain methods should be treated similar to a
constructor in the sense that they always run before other methods. Such
examples are JUnit setUp methods but also @PostConstruct methods.

Consider the following case:
- tests and the code under test are in the same project (Maven default)
- tests and the code under test are in the same package (Maven default
and handy for things like package default visibility)
- @NonNullByDefault on the package
- a test that look like this

public class ATest {

private SomeType object;

@Before
public void setUp() {
object = new SomeType();
}

@Test
public void aMethod() {
assertNotNull(object.aMethod());
}

}

This test is null safe because the @Before method runs after the
constructor and before every other method but null analysis does not
seem to understand this. In this case the problem could be solved by
initializing in the declaration. But sometimes the set up is more
involved and you want it in a dedicated method.

Are there any workarounds like disabling null analysis for certain
source folders or classes?

Cheers
Philippe

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Re: Null Analysis and Unit Tests [message #1220575 is a reply to message #1219196]

Thu, 12 December 2013 15:22

Philippe Marschall

Messages: 121
Registered: July 2009

Senior Member

On 02.12.13 16:24, Philippe Marschall wrote:
> Hi
>
> We're evaluating the null analysis in JDT and we encountered some issues
> that are annoying in unit tests. The cause is that null analysis doesn't
> seem to understand that certain methods should be treated similar to a
> constructor in the sense that they always run before other methods. Such
> examples are JUnit setUp methods but also @PostConstruct methods.
>
> Consider the following case:
> - tests and the code under test are in the same project (Maven default)
> - tests and the code under test are in the same package (Maven default
> and handy for things like package default visibility)
> - @NonNullByDefault on the package
> - a test that look like this
>
> public class ATest {
>
> private SomeType object;
>
> @Before
> public void setUp() {
> object = new SomeType();
> }
>
> @Test
> public void aMethod() {
> assertNotNull(object.aMethod());
> }
>
> }
>
> This test is null safe because the @Before method runs after the
> constructor and before every other method but null analysis does not
> seem to understand this. In this case the problem could be solved by
> initializing in the declaration. But sometimes the set up is more
> involved and you want it in a dedicated method.
>
> Are there any workarounds like disabling null analysis for certain
> source folders or classes?

*bump*

Cheers
Philippe

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Re: Null Analysis and Unit Tests [message #1238652 is a reply to message #1220575]

Sun, 02 February 2014 01:05

Stephan Herrmann

Messages: 1853
Registered: July 2009

Senior Member

Sorry for the delay in answering (we are more than busy getting JDT ready for Java 8 ).

The question you ask poses some difficulties:

Null analysis for fields is not at all straight forward. To help the compiler really understanding your scheme of initialization more annotations need to be included in the analysis (which we cannot offer within the Luna time frame). I don't think JUnit's @Before annotation would be first on our list, because avoiding NPE in an application seems more relevant than avoiding NPE in tests Smile

Of course there are means to suppress warnings (and if suppressing optional errors is enabled: errors, too) at several levels. You can ignore all optional problems per source folder, or you could simply add @SuppressWarnings("null") to your test class.

Stephan

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Re: Null Analysis and Unit Tests [message #1278372 is a reply to message #1238652]

Thu, 27 March 2014 08:36

Philippe Marschall

Messages: 121
Registered: July 2009

Senior Member

On 02.02.14 02:05, Stephan Herrmann wrote:
> Sorry for the delay in answering (we are more than busy getting JDT
> ready for Java 8 ).
>
> The question you ask poses some difficulties:
>
> Null analysis for fields is not at all straight forward. To help the
> compiler really understanding your scheme of initialization more
> annotations need to be included in the analysis (which we cannot offer
> within the Luna time frame). I don't think JUnit's @Before annotation
> would be first on our list,

Fair enough. What about @PostConstruct? Yes, that would require a change
to JUnit to support @PostConstruct (and @PreDestroy) but that may be
better in the long run anyway.

> because avoiding NPE in an application seems
> more relevant than avoiding NPE in tests :)
>
> Of course there are means to suppress warnings (and if suppressing
> optional errors is enabled: errors, too) at several levels. You can
> ignore all optional problems per source folder, or you could simply add
> @SuppressWarnings("null") to your test class.

Ok.

Cheers
Philippe

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