Software craftsman, author of Software Craftsmanship: Professionalism Pragmatism Pride (http://leanpub.com/socra) and founder of the London Software Craftsmanship Community (LSCC). Sandro started coding at a very young age but just started his professional career years later, in 1996. He has worked for startups, software houses, product companies and a few international consultancy companies. Having worked as a consultant for the majority of his career, he had the opportunity to work in a good variety of projects, different languages, technologies and industries. Currently he is a director and a software craftsman at UBS Investment Bank, where he writes code, look after the quality of the applications, mentor developers and help teams around the world to get better at delivering quality software. Sandro is a DZone MVB and is not an employee of DZone and has posted 34 posts at DZone. You can read more from them at their website. View Full User Profile

Testing Multiple Properties With a Single Assertion

05.28.2012
| 3942 views |
  • submit to reddit
Every time I was trying to test an object's properties I was neither satisfied writing very verbose tests nor in using some of the out of the box hamcrest matchers. Although using the matchers was a big help, I never managed to make them read the way I wanted.

Another thing that was very important to me, I wanted to have a single assertion per method and a very descriptive description if the test did not pass.

I've decided to write my own matcher and hopefully it will be useful to other people. So, that's what I've done:

BeanMatcher

Hamcrest matcher to match multiple attributes of an object within a single assertion.

How to use it

// Static imports
    
    import static org.craftedsw.beanpropertymatcher.matcher.BeanMatcher.has;
    import static org.craftedsw.beanpropertymatcher.matcher.BeanPropertyMatcher.property;
    import static org.hamcrest.MatcherAssert.assertThat;
    import static org.hamcrest.Matchers.equalTo;
    import static org.hamcrest.Matchers.greaterThan;

    // Imagine that you have a method that returns an object Person

    Person person = new Person();
    person.setFirstName("Sandro");
    person.setAge(25);
    person.setLastName("Mancuso");
    
    // Then you can test it like that
    
    assertThat(person, has(
                            property("firstName", equalTo("Another dude")), // Mistmatch
                            property("age", greaterThan(18)), // Use any matcher
                            property("lastName", equalTo("Mancuso"))));

NOTE: Make sure you are using org.hamcrest.MatcherAssert.assertThat instead of the JUnit one.

If you run this test, you will get a message like

java.lang.AssertionError:
        Expected: property "firstName" = "Another dude"
        but: property "firstName" was "Sandro"

Now, change the age check to 

   property("age", greaterThan(60)) 

And you should get:

java.lang.AssertionError:
        Expected: property "firstName" = "Another dude" , property "age" = a value greater than <60>
        but: property "firstName" was "Sandro" , property "age" <25> was less than <60>

 

Testing object graphs

You can also do this

Person person = new Person();
    person.setFirstName("Sandro");
    person.setAge(35);
        
    Country uk = new Country();
    uk.setName("United Kingdom");
        
    Address address = new Address();
    address.setPostcode("1234556");
    address.setCity("London");
    address.setCountry(uk);
        
    person.setAddress(address);
        
    assertThat(person, has(
                            property("firstName", equalTo("Sandro")),
                            property("age", greaterThan(18)),
                            property("address.city", equalTo("London")),
                            property("address.postcode", equalTo("1234556")),
                            property("address.country.name", equalTo("United Kingdom")))); 

I use a combination of two matchers to do that:
- BeanMatcher: Provides the "has" method responsible to group all the property matchers.
- BeanPropertyMatcher: Provides the "property" method.

I expect to make more changes to them, so for the most up-to-date version, please check BeanMatcher on my github account.
 

 

 

Published at DZone with permission of Sandro Mancuso, author and DZone MVB. (source)

(Note: Opinions expressed in this article and its replies are the opinions of their respective authors and not those of DZone, Inc.)

Comments

Daniel Slazer replied on Tue, 2012/06/12 - 12:32pm

Got your point mate. Since you can change the value of existing element, this is really not a readonly List rather a Fixed size List. Thanks

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.