The JSON argument sources let you provide arguments for parameterized tests from JSON. There are three annotations:

  • @JsonSource for lenient inline JSON

  • @JsonFileSource for JSON files from the local file system

  • @JsonClasspathSource for JSON files from the classpath

There are various ways how the method arguments for a single parametrized test are provided. By default the root of the source will be treated as candidate for the test arguments. If the root is an object then the entire object will be one argument, if the root is an array then every element of the array will be one argument.

It is also possible to use a nested array from the provided JSON to access the source for the test arguments. The JsonFileSource#data can be used to tell the extraction mechanism to use the element with that name to look for the source of the data.

Depending on the test method parameters, the extraction of the values might differ.

Method Arguments

Single Argument Methods

If the method has a single argument, the JSON object argument will be converted to that type.

Argument type
public class Jedi {

    public String name;
    public String height;

    @Override
    public String toString() {
        return "Jedi {" + "name='" + name + '\'' + ", height=" + height + '}';
    }

}
JSON Source File
[
  {
    "name": "Luke",
    "height": 172
  },
  {
    "name": "Yoda",
    "height": 66
  }
]
@ParameterizedTest
@JsonClasspathSource("jedis.json")
void singleJedi(Jedi jedi) {
    // YOUR TEST CODE HERE
}
@ParameterizedTest
@JsonSource("["
        + "  { name: 'Luke', height: 172  },"
        + "  { name: 'Yoda', height: 66 }"
        + "]")
void singleJedi(Jedi jedi) {
    // YOUR TEST CODE HERE
}

This parametrized test will generate the following test executions:

  • [1] Jedi {name='Luke', height=172}

  • [2] Jedi {name='Yoda', height=66}

It is also possible to extract only a single element from each argument object by using the @Property annotation.

@ParameterizedTest
@JsonClasspathSource("jedis.json")
void singleJediProperty(@Property("name") String jediName) {
    // YOUR TEST CODE HERE
}
@ParameterizedTest
@JsonSource({
        "{ name: 'Luke', height: 172  }",
        "{ name: 'Yoda', height: 66 }"
})
void singleJediProperty(@Property("name") String jediName) {
    // YOUR TEST CODE HERE
}

This parametrized test will generate the following tests:

  • [1] Luke

  • [2] Yoda

Multiple Argument Methods

If the method has multiple arguments, each JSON object argument will be deconstructed to each of the method arguments. By default, the method argument name will be used for locating the element that needs to be taken from the JSON object. You can also use @Property to give the name of the element that needs to be extracted.

Important

If your test sources are not compiled using the --parameters flag then the names of the arguments will not be like they are written in the source code. In that the situation you need to use @Property instead.

Using the same jedis.json and the following test

@ParameterizedTest
@JsonClasspathSource("jedis.json")
void deconstructFromArray(@Property("name") String name, @Property("height") int height) {
    // YOUR TEST CODE HERE
}
@ParameterizedTest
@JsonSource({
        "{ name: 'Yoda', height: 66 }",
        "{ name: 'Luke', height: 172 }",
})
void deconstructFromArray(@Property("name") String name, @Property("height") int height) {
    // YOUR TEST CODE HERE
}
// @formatter:on

This parametrized test will generate the following tests:

  • [1] Luke, 172

  • [2] Yoda, 66

Extracting nested array

Sometimes we want to extract a nested array instead of the root element. For this purpose JsonClasspathSource#data can be used.

Jedi with nested array
{
  "name": "Luke",
  "height": 172,
  "vehicles": [
    {
      "name": "Snowspeeder",
      "length": 4.5
    },
    {
      "name": "Imperial Speeder Bike",
      "length": 3
    }
  ]
}

Here we want to test the vehicles. The test for this will look like:

@ParameterizedTest
@JsonClasspathSource(value = "luke.json", data = "vehicles")
void lukeVehicles(@Property("name") String name, @Property("length") double length) {
    // YOUR TEST CODE HERE
}

This parametrized test will generate the following tests:

  • [1] Snowspeeder, 4.5

  • [2] Imperial Speeder Bike, 3

Thread-Safety

This extension is safe to use during parallel test execution.

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