Spock test if method was called by constructor - firebase-realtime-database

Question

I have a Firebase admin helper class that I am testing with Spock. The constructor of this class will call another method in the class to initialize certain fields if it has to, as shown below:
public class FirebaseUtility {
private static FirebaseDatabase db = null;
public FirebaseUtility() throws IOException {
if (db == null) {
initializeFirebase();
}
}
public void initializeFirebase() throws IOException {
InputStream serviceAccount = ClassLoader.getSystemResourceAsStream("serviceAccount.json");
FirebaseOptions options = new FirebaseOptions.Builder()
.setCredentials(GoogleCredentials.fromStream(serviceAccount))
.setDatabaseUrl("<my_database_url>").build();
FirebaseApp.initializeApp(options);
db = FirebaseDatabase.getInstance();
}
}
Basically, there is no point in doing all the initialization code if the FirebaseDatabase is already set.
I have tried doing this, but it does not seem to work:
class FirebaseUtilitySpec extends Specification {
def "instantiating FirebaseUtility should run initialization code"() {
given:
def f
when:
f = new FirebaseUtility()
then:
1 * f.initializeFirebase()
}
}

Answer 1

First of all, you cannot check interactions on original objects, you need to use a mock or spy. Furthermore, those types of objects cannot intercept interactions on static methods or constructors. For that you would have to add Mockito or even PowerMock to the mix. But basically, static methods are just ugly anyway and initialising a static member in a constructor call is not necessary. Just use a lazy getter for the database object and intercept its behaviour.
I have simplified your example a bit, removing the external dependency and just emulating Firebase so as to make it easier to answer with an MCVE:
package de.scrum_master.stackoverflow;
public class FirebaseDatabase {
private static FirebaseDatabase instance;
public static FirebaseDatabase getInstance() {
if (instance == null)
instance = new FirebaseDatabase();
return instance;
}
}
package de.scrum_master.stackoverflow;
public class FirebaseUtility {
private static FirebaseDatabase db = null;
public FirebaseDatabase getDb() {
if (db == null)
initializeFirebase();
return db;
}
protected void initializeFirebase() {
db = FirebaseDatabase.getInstance();
}
}
package de.scrum_master.stackoverflow
import spock.lang.Specification
class FirebaseUtilitySpec extends Specification {
def "instantiating FirebaseUtility runs initialization code exactly once"() {
given:
FirebaseUtility f = Spy()
when:
f.getDb()
then:
1 * f.initializeFirebase()
when:
f.getDb()
then:
0 * f.initializeFirebase()
}
}