Can Spock Mock a Java constructor

Question

Trying to broaden the appeal of Spock at work and run into this issue. Actually trying to write Unit Tests for a Groovy class, but one that calls out to Java. A static method calls a private constructor. The code looks like:

private MyConfigurator(String zkConnectionString){
    solrZkClient = new SolrZkClient(zkConnectionString, 30000, 30000,
            new OnReconnect() {
                @Override
                public void command() { . . . }
            });
}

"SolrZkClient" is from third party (Apache) Java library. Since it tries to connect to ZooKeeper, I would like to mock that out for this Unit Test (rather than running one internally as part of the unit test).

My test gets to the constructor without difficulty, but I can't get past that ctor:

def 'my test'() {
    when:
        MyConfigurator.staticMethodName('hostName:2181')
    then:
        // assertions
}

Is there anyway to do this?

Answer 1

Since the class under test is written in Groovy, you should be able to mock the constructor call by way of a global Groovy Mock/Stub/Spy (see Mocking Constructors in the Spock Reference Documentation). However, a better solution is to decouple the implementation of the MyConfigurator class, in order to make it more testable. For example, you could add a second constructor and/or static method that allows to pass an instance of SolrZkClient (or a base interface, if there is one). Then you can easily pass in a mock.

Answer 2

You can use GroovySpy for mocking constructors in Spock

For example:

def 'my test'() {
 given: 
 def solrZkClient = GroovySpy(SolrZkClient.class,global: true);
 when:
    MyConfigurator.staticMethodName('hostName:2181')
 then:
    // assertions
}