Unit testing using JSONassert library

In this article, we’ll have a closer look at a library called JSONassert library. We will explain using some examples and how this library can be used. So, let’s get started!

Working with an easy example:

Let’s start our tests with a simple JSON string comparison:

String actual = "{objectId:123, name:\"magy\",lastName:\"henry\"}"; String expected="{objectId:123,name:\"magy\"}"; JSONAssert.assertEquals(expected, actual, false);
The above example will work for the condition strict=false. However, if it is set to true, the test will fail. You have to keep in mind, that JSONAssert makes a logical comparison of the data. This means that the ordering of elements does not matter while dealing with JSON objects.
Working with a complex example

Assuming, that you want a unit test where you have to validate (match an actual response with expected) our rest interfaces in the JUnit. Our endpoint delivers a list of objects. So, the goals are to verify the properties of each object. Let’s assume that delivered response is a list of a type called partner, where the implementation of the class partner is as following:

@Data
public class Partner {
    private String id;    private String firstName;    private String lastName;    private LocalDate birthDate;    private Gender gender;    private MaritalStatus maritalStatus;    private String phoneNumber;
}

The following Java examples will help you to understand the usage of. Assuming, we need to write some assertions for each family member on the list. So, the following should be done.

ResponseEntity<List<Partner>> response = restTemplate.exchange(    "http://localhost:8080/partners/x/family",    HttpMethod.GET,    null,
    new ParameterizedTypeReference<List<Partner>>(){});
List<Parnter> partners= response.getBody();
//Now we need to test that each partner in the family has a certain values.
Parnter partner1= partners.stream.filter(partner -> parnter.getid().equals("1")).findFirst().get();
assertEquals("Magy", partner1.getFirstName());
assertEquals("Mueller", partner1.getLastName());
assertEquals(of(1980, 7, 12), partner1.getBirthDate());
assertEquals(FEMALE, partner1.getGender());
assertNull(partner1.getMaritalStatus());

// Testing the second person
Parnter partner2= partners.stream.filter(partner -> parnter.getid().equals("2")).findFirst().get();
assertEquals("Marc", partner2.getFirstName());
assertEquals("Ullenstein", partner2.getLastName());
assertEquals(of(1988, 7, 13), partner2.getBirthDate());
assertEquals(MALE, partner2.getGender());
assertNull(partner1.getMaritalStatus());

So, to test the values for just one partner, it takes some time. So, in case of testing multiple partners, it will take a lot of code lines. We would like to use JSONAssert. To make it easier using JSONAssert, let’s create a JSON file under test/resources/json in which we create a list of objects, where each object contains the properties, that will be tested. You should also have in mind, that this library allows developers not to have a restrict mode, which means that you don’t have to test against each property.

String actual= restTemplate.getForObject("http://localhost:8080/partners/x/family", String.class);
String expected = IOUtils.toString(this.getClass().getResourceAsStream("/json/expectedJsonResponse.json"),"UTF-8");
JSONAssert.assertEquals(expected, actual, false);

The above method takes three parameters as seen in the above example, where the first parameter is the expected JSON. The second one is the result, or what we got as a response from our endpoint. The third one defines whether we should use the strict mode or not. When comparing the code written in both cases, you are going to think about why you should use this library in the future. You can give up all of the used assertions in the above example.

Conclusion
In this article, we looked at multiple scenarios in which JSONAssert can be helpful. We started with a very simple example and moved on to more complex comparisons. And, as always, stay tuned for new interesting articles.