[Nerthus]

Timo is right about this, it was politically motivated and not a simple test. Hitler had made an agreement with Franco - Germany would receive necessary war material such as iron or copper but would support him in change in his war actions. First the Germans helped him take hold of Bilbao, a quite strategic point. The air force power of Franco's nationalists was a joke. He couldn't handle the Basque resistance by himself although he had put a vast region of Spain under his control before, so he asked for Hitler's help to loan him his bombers and fighters. Wolfram Von Richthofen was put in charge of the Condor Legion but Guernica was bombed on behalf of Franco, as a wanted to show clear sign that the military power of the nationalists was stronger than that of the republicans (btw I am talking about the Spanish civil war).
Later Hitler regretted his alliance with Franco, as his demands proved to be too many and crossed the line after him joining the Anticomintern Pact in 1938 and in the end no more agreement was reached. Hitler said he would have rather had "two or three teeth pulled out" before trying to negotiate with Franco again.