Salesforce trailhead - Apex-Integration-Services-Apex-REST-Callouts

AnimalLocator.cls

public class AnimalLocator {
	public class cls_animal {
		public Integer id;	
		public String name;	
		public String eats;	
		public String says;	
	}    
public class JSONOutput{
	public cls_animal animal;

   	//public JSONOutput parse(String json){
	//return (JSONOutput) System.JSON.deserialize(json, JSONOutput.class);
	//}
}
    
    public static String getAnimalNameById (Integer id) {
        Http http = new Http();
        HttpRequest request = new HttpRequest();
        request.setEndpoint('https://th-apex-http-callout.herokuapp.com/animals/' + id);
        //request.setHeader('id', String.valueof(id)); -- cannot be used in this challenge :)
        request.setMethod('GET');
        HttpResponse response = http.send(request);
        system.debug('response: ' + response.getBody());
        //Map<String,Object> map_results = (Map<String,Object>) JSON.deserializeUntyped(response.getBody());
        jsonOutput results = (jsonOutput) JSON.deserialize(response.getBody(), jsonOutput.class);
        //Object results = (Object) map_results.get('animal');
		system.debug('results= ' + results.animal.name);
        return(results.animal.name);
    }

}

AnimalLocatorMock

@IsTest
global class AnimalLocatorMock implements HttpCalloutMock {
    
    global HTTPresponse respond(HTTPrequest request) {
        Httpresponse response = new Httpresponse();
        response.setStatusCode(200);
        //-- directly output the JSON, instead of creating a logic
        //response.setHeader('key, value)
        //Integer id = Integer.valueof(request.getHeader('id'));
        //Integer id = 1;
        //List<String> lst_body = new List<String> {'majestic badger', 'fluffy bunny'};
        //system.debug('animal return value: ' + lst_body[id]);
        response.setBody('{"animal":{"id":1,"name":"chicken","eats":"chicken food","says":"cluck cluck"}}');
        return response;
    }

}

AnimalLocatorTest.cls

@IsTest
public class AnimalLocatorTest {
    @isTest
    public static void testAnimalLocator() {
        Test.setMock(HttpCalloutMock.class, new AnimalLocatorMock());
        //Httpresponse response = AnimalLocator.getAnimalNameById(1);
        String s =  AnimalLocator.getAnimalNameById(1);
        system.debug('string returned: ' + s);
    }

}

This does the job

`
public class AnimalLocator {
public static String getAnimalNameById(Integer id) {
String endpoint = 'https://th-apex-http-callout.herokuapp.com/animals/' + id;
HttpRequest req = new HttpRequest();
req.setEndpoint(endpoint);
req.setMethod('GET');

    Http http = new Http();
    HttpResponse res = http.send(req);
    if (res.getStatusCode() == 200) { 
        Map<String, Object> jRes = (Map<String, Object>) JSON.deserializeUntyped(res.getBody());
        Map<String, Object> animal = (Map<String, Object>) jRes.get('animal');
        String animalName = (String) animal.get('name');
        return animalName;
    } else {
        return null;
    }
}

}
`

Thank you for the post. I was able to find my error in my AnimalLocatorTest class checking against your code.