Added unit test for Descriptor of IssuesRecorder.

src/test/java/io/jenkins/plugins/analysis/core/steps/IssuesRecorderTest.java

@@ -0,0 +1,27 @@
+package io.jenkins.plugins.analysis.core.steps;
+
+import org.junit.jupiter.api.Test;
+
+import io.jenkins.plugins.analysis.core.steps.IssuesRecorder.Descriptor;
+import static io.jenkins.plugins.analysis.core.testutil.FormValidationAssert.assertThat;
+
+import hudson.util.FormValidation;
+
+/**
+ * @author Arne Schöntag
+ */
+class IssuesRecorderTest {
+
+    @Test
+    void shouldBeOkIfEncodingIsEmpty(){
+        //given
+        Descriptor descriptor = new Descriptor();
+
+        //when
+        FormValidation acturalResult = descriptor.doCheckSourceCodeEncoding("");
+
+        //then
+        assertThat(acturalResult).isOk();
+    }
+
+}