Sources of Arguments in Parameterized Tests

Learn how to create sources of arguments in JUnit 5.


We’ve discussed built-in sources of parameters for parameterized tests. We can also create new sources of arguments using the @ArgumentsSource annotation and the org.junit.jupiter.params.provider.ArgumentsProvider interface. The @ArgumentsSource annotation specifies the implementation of ArgumentsProvider to use for providing the arguments. The ArgumentsProvider only has one method, Stream<? extends Arguments> provideArguments(ExtensionContext context) throws Exception, to return a stream of Arguments objects.

The @JsonFileSource annotation

To demonstrate custom sources of arguments, we’ll create a source of arguments that resolves JSON file arguments. The JSON file should contain an array of objects. Each object in the array is mapped to an Arguments object. Because the properties in a JSON object aren’t ordered, we need to specify the mapped property name for each parameter.

The @JsonFileSource annotation uses @ArgumentsSource to specify the JsonArgumentsProvider implementation class.

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