How should I test my external dependencies?

[gdamoreira]

Hi team,

I'm using FnProject now and I'm using external dependencies to access external resources and I'm trying to mock to test the function without dependencies in it. How should I mock my external resource?

public class FunctionTest {

    @Rule
    public final FnTestingRule testing = FnTestingRule.createDefault();

    @Test
    public void shouldReturnGreeting() {
        testing.givenEvent().withBody("{\"data\":123}").enqueue();
        testing.thenRun(Function.class, "handleRequest");

        FnResult result = testing.getOnlyResult();
        assertEquals("OK", result.getBodyAsString());
    }

}

public class Function {
    public ExternalResource getExternalResource() {
        return new ExternalResource(); // how to mock this?
    }
    public String handleRequest(String inputData) {
        var externalResource = getExternalResource();
        externalResource.doSomething();
        return "OK";
    }
}