jUnit:NPE on private member initialization

Question

Have jUnit test, which initializes my bean:

ShowProducts sp = new ShowProducts();

got NullPointerException on following line in ShowProducts.java:

    private Locale locale = FacesContext.getCurrentInstance().getViewRoot()
                .getLocale();

...
    public Locale getLocale() {
        return locale;
    }

    public String getLanguage() {
        return locale.getLanguage();
    }

    public void localize() {
        String localeParam = FacesContext.getCurrentInstance()
                .getExternalContext().getRequestParameterMap().get("lang");
        locale = new Locale(localeParam);
        FacesContext.getCurrentInstance().getViewRoot().setLocale(locale);
    }

How to initialize properly this field in test?

EDIT:

faces-config:

<application>
    <locale-config>
        <default-locale>ru</default-locale>
        <supported-locale>ua</supported-locale>
    </locale-config>
    <resource-bundle>
        <base-name>msg</base-name>
        <var>m</var>
    </resource-bundle>
</application>

.xhtml:

    <h:form>
        <h:commandLink action="#{showProducts.localize}" includeViewParams="true"
                       rendered="#{showProducts.language=='ua'}">
            #{m.rus}.
            <f:param name="lang" value="ru"/>
        </h:commandLink>
        <h:commandLink action="#{showProducts.localize}" includeViewParams="true"
                       rendered="#{showProducts.language=='ru'}">
            #{m.ukr}.
            <f:param name="lang" value="ua"/>
        </h:commandLink>
    </h:form>

Answer 1

Apparently your JSF FacesContext is not configured properly (I do no know much about faces, but I assume that setting them up and running in jUnit test is pretty complicated). However, there is help underway - use mocking.

In your test case, you like to assure that: - ShowProducts retrieves proper locale out of faces context / view root - does other things properly.

I recommend you to use jmockit. Your test case would become something like:

 @Test
 public void testShowProducts(@Cascading final FacesContext facesContext) {
        final Locale locale = new Locale(...)
        new Expectations() {
           {
              FacesContext.FacesContext.getCurrentInstance().getViewRoot().getLocale();
              returns(locale);
           }


        };
       ShowProducts sp = new ShowProducts();

       ...  do your assertions other stuff there
 }

This techuique is applicable to lot of contextes and simplifies test code greatly.

Answer 2

Accessing static methods makes writing tests hard.

Either pass the Locale with the constructor or use a setter.

The easiest change would be to add a second constructor with a Locale as parameter and use it for the unittest. The default constructor then initializes the field from the FacesContext.

Towards a cleaner design you should extract a Localizer where you handle all the localization, so to separate then ShowProducts which doesn't need the FacesContext from the Localizer which does.

The Localizer would be something like:

public class Localizer {
    public void localize() {
        String localeParam = FacesContext.getCurrentInstance()
                .getExternalContext().getRequestParameterMap().get("lang");
        locale = new Locale(localeParam);
        FacesContext.getCurrentInstance().getViewRoot().setLocale(locale);
    }
}

This has nothing to do with ShowProducts. Not sure what you need getLanguge() for.