Added test for project variable details (#387).

Author: gmessner

src/test/java/org/gitlab4j/api/TestGitLabApiBeans.java

@@ -333,6 +333,12 @@ public void testProjectEvents() throws Exception {
         assertTrue(compareJson(events, "project-events.json"));
     }
 
+    @Test
+    public void testProjectVariableDetails() throws Exception {
+        Variable variable = unmarshalResource(Variable.class, "project-variable-details.json");
+        assertTrue(compareJson(variable, "project-variable-details.json"));
+    }
+
     @Test
     public void testProtectedBranch() throws Exception {
         ProtectedBranch protectedBranch = unmarshalResource(ProtectedBranch.class, "protected-branch.json");

src/test/resources/org/gitlab4j/api/project-variable-details.json

@@ -0,0 +1,7 @@
+{
+    "key": "TEST_VARIABLE_1",
+    "variable_type": "env_var",
+    "value": "TEST_1",
+    "protected": false,
+    "masked": true
+}