Add unit tests for XmlFileSource

build.gradle

@@ -49,6 +49,8 @@ dependencies {
     testCompile(
             'org.codehaus.groovy:groovy-all:2.5.3',
             'org.spockframework:spock-core:1.2-groovy-2.5',
-            "io.projectreactor:reactor-test:${reactorVersion}"
+            "io.projectreactor:reactor-test:${reactorVersion}",
+            'net.bytebuddy:byte-buddy:1.9.2',
+            'org.objenesis:objenesis:3.0.1'
     )
 }

src/test/groovy/io/github/aplotnikov/batch/processing/reactor/source/XmlFileSourceSpec.groovy

@@ -0,0 +1,35 @@
+package io.github.aplotnikov.batch.processing.reactor.source
+
+import reactor.core.publisher.Flux
+import reactor.test.StepVerifier
+import spock.lang.Specification
+import spock.lang.Subject
+
+class XmlFileSourceSpec extends Specification {
+
+    Repository repository = Mock()
+
+    Queue queue = Mock()
+
+    @Subject
+    XmlFileSource source = new XmlFileSource(repository, queue)
+
+    void 'should merge results from DB and from queue'() {
+        given:
+            String fileFromDB = 'file_from_db.xml'
+        and:
+            String fileFromQueue = 'file_from_queue.xml'
+        when:
+            Flux<String> files = source.readAll()
+        then:
+            StepVerifier.create(files)
+                    .expectNext(fileFromDB)
+                    .expectNext(fileFromQueue)
+        and:
+            1 * repository.readAll() >> Flux.just(fileFromDB)
+        and:
+            1 * queue.poll() >> Flux.just(fileFromQueue)
+        and:
+            0 * _
+    }
+}