Fix malfunctioning tests

Fix testDoFilterWithExistingProjectAndPackage test by adding a missing
line which adds a mock project to the cache. Without this line, the test
will assume that the entire string used is a valid project which is not
the case (The extra is meant to represent a package, not a project).
This fix is based on the changes made on the parent commit.

Fix testDoFilterWithNonExistingProject test by using empty option.
Optional.of does not work with null values and will throw a
NullPointerException when the argument is null. empty returns an empty
Optional value best representing the test case of a non existing
project.

Bug: Issue 12454
Change-Id: I356751bec4ccb6f44226219c9ae7b41e7dc02cd7

src/test/java/com/ericsson/gerrit/plugins/goimport/GoImportFilterTest.java

diff --git a/src/test/java/com/ericsson/gerrit/plugins/goimport/GoImportFilterTest.java b/src/test/java/com/ericsson/gerrit/plugins/goimport/GoImportFilterTest.java
index 39f01df..1bea7b6 100644
--- a/src/test/java/com/ericsson/gerrit/plugins/goimport/GoImportFilterTest.java
+++ b/src/test/java/com/ericsson/gerrit/plugins/goimport/GoImportFilterTest.java
@@ -91,7 +91,6 @@
     unitUnderTest = new GoImportFilter(mockAnonProvider, mockPerms, mockProjectCache, PROD_URL);
     assertThat(unitUnderTest).isNotNull();
     when(mockResponse.getOutputStream()).thenReturn(mockOutputStream);
-
     when(mockAnonProvider.get()).thenReturn(mockAnon);
     when(mockPerms.user(mockAnon)).thenReturn(mockPermsWithUser);
     when(mockPermsWithUser.ref(any())).thenReturn(mockPermsForRef);
@@ -171,6 +170,8 @@
   public void testDoFilterWithExistingProjectAndPackage() throws Exception {
     when(mockRequest.getServletPath()).thenReturn("/" + PROJECT_NAME + "/my/package");
     when(mockRequest.getParameter("go-get")).thenReturn("1");
+    when(mockProjectCache.get(Project.nameKey(PROJECT_NAME)))
+        .thenReturn(Optional.of(mockProjectState));
     when(mockPermsForRef.testOrFalse(RefPermission.READ)).thenReturn(false);
     unitUnderTest.doFilter(mockRequest, mockResponse, mockChain);
     verify(mockOutputStream, times(1)).write(response200(false, false));
@@ -198,7 +199,7 @@
   public void testDoFilterWithNonExistingProject() throws Exception {
     when(mockRequest.getServletPath()).thenReturn("/" + PROJECT_NAME);
     when(mockRequest.getParameter("go-get")).thenReturn("1");
-    when(mockProjectCache.get(any(Project.NameKey.class))).thenReturn(null);
+    when(mockProjectCache.get(any(Project.NameKey.class))).thenReturn(Optional.empty());
     unitUnderTest.doFilter(mockRequest, mockResponse, mockChain);
     verify(mockOutputStream, times(1)).write(any(byte[].class));
     verify(mockChain, times(0)).doFilter(mockRequest, mockResponse);