Add unit tests for ExternalAPIUtil

-Add unit tests for ExternalAPIUtil
-Add dependency injection via constructor
-Add factory for creating ExternalAPIUtil and RESTClient

Change-Id: Ied89afa3612de8d51424c95239341a57387ad94f
Issue-ID: SO-1195
Signed-off-by: Michal Kabaj <michal.kabaj@nokia.com>
diff --git a/bpmn/so-bpmn-building-blocks/pom.xml b/bpmn/so-bpmn-building-blocks/pom.xml
index 8f1f2bf..4fe02ee 100644
--- a/bpmn/so-bpmn-building-blocks/pom.xml
+++ b/bpmn/so-bpmn-building-blocks/pom.xml
@@ -107,6 +107,12 @@
 			<scope>test</scope>
 		</dependency>
 		<dependency>
+			<groupId>org.assertj</groupId>
+			<artifactId>assertj-core</artifactId>
+			<version>1.7.0</version>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-test</artifactId>
 			<scope>test</scope>