Added test to explain usage of Swagger Codegen with Retrofit

Author: cortinico

samples/generated-code/build.gradle

@@ -46,6 +46,9 @@ dependencies {
     // RxJava
     implementation "io.reactivex.rxjava2:rxjava:2.2.4"
     implementation "io.reactivex.rxjava2:rxandroid:2.1.0"
+
+    // JUnit4
+    testImplementation "junit:junit:4.12"
 }
 
 generateSwagger {

samples/generated-code/src/test/java/com/yelp/codegen/generatecodesamples/InvokeRetrofitTest.kt

@@ -0,0 +1,26 @@
+package com.yelp.codegen.generatecodesamples
+
+import com.yelp.codegen.generatecodesamples.apis.DefaultApi
+import com.yelp.codegen.generatecodesamples.tools.GeneratedCodeConverters
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import retrofit2.Retrofit
+import retrofit2.adapter.rxjava2.RxJava2CallAdapterFactory
+
+class InvokeRetrofitTest {
+
+    @Test
+    fun createAndInvokeRetrofit() {
+        val retrofit: Retrofit = Retrofit.Builder()
+                .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
+                .addConverterFactory(GeneratedCodeConverters.converterFactory())
+                .baseUrl("https://petstore.swagger.io/v2/")
+                .build()
+
+        val defaultApi = retrofit.create(DefaultApi::class.java)
+        val pet = defaultApi.getPetById(1).blockingGet()
+
+        println(pet)
+        assertEquals(1L, pet.id)
+    }
+}