As we discussed in our previous article about Solr with Scala and AkkaHttp, we have used Solr as a service and tried to hit the Solr service with AkkaHttp and spray routes. 

When we want to test methods that are creating connections with a remote Solr server, we have to use Embedded Solr.

What Is Embedded Solr?

Embedded Solr has the same interface as Solr without requiring an HTTP connection. When we “embed” Solr into a Java an application, it provides the exact same API that you would use if you were connecting to a remote Solr instance. We can use embedded Solr for in-memory testing because when we implement test cases, it should not depend on any external resources.

How to Use Embedded Solr

When we wish to use Embedded Solr, we have to follow some basic steps for creating an interface with it.

1. Add the Solr-Core dependency.
2. Follow this predefined directory structure:

   solr
     |-test_embedded //name of configuration folder
            |-conf
                |-lang
                |-currency.xml
                |-elevate.xml         
                |-managed-schema
                |-param-.json
                |-protword.txt
                |-solrconfig.xml
                |-stopwords.txt
                |-synonyms.txt
            |-data (Optional if not created than it will create automatically)
            |-core.properties
     |-solr.xml

3. Now, we are ready to start Embedded Solr in the test set-up. It will shut down it after completes testing.

   override def before() = {
    val container = new CoreContainer()
    container.load()
    server = new EmbeddedSolrServer(container, "test_embedded")
   }
   
   test("test embedded solr"){
     val solrInputDocument = new SolrInputDocument()
     solrInputDocument.addField("id", 1)
     solrInputDocument.addField("name", "test")
     server.add("test_embedded",solrInputDocument)
   
     val parameter = new SolrQuery()
     parameter.set("q", "*:*")
     val result = server.query("test_embedded",parameter)
     val docList = result.getResults()
     val doc = docList.get(0)
     assert(doc.getFirstValue("name").toString().toLowerCase().contains("test"));
   }
   
   override def afterAll(): Unit = {
    server.close
   }

This is a basic code example for testing Embedded Solr. If test case passes successfully, we are ready to test the services. For more examples and code, please refer to the Knoldus GitHub page.