diff --git a/lib/taskana-core/src/main/java/pro/taskana/report/structure/Report.java b/lib/taskana-core/src/main/java/pro/taskana/report/structure/Report.java
index 2fa2ee48c..2e3b849a0 100644
--- a/lib/taskana-core/src/main/java/pro/taskana/report/structure/Report.java
+++ b/lib/taskana-core/src/main/java/pro/taskana/report/structure/Report.java
@@ -21,15 +21,15 @@ import pro.taskana.impl.report.row.SingleRow;
  */
 public abstract class Report<I extends QueryItem, H extends ColumnHeader<? super I>> {
 
-    protected List<H> columnHeaders = new ArrayList<>();
+    protected List<H> columnHeaders;
     private Map<String, Row<I>> reportRows = new LinkedHashMap<>();
     private Row<I> sumRow;
     private String rowDesc;
 
     protected Report(List<H> columnHeaders, String rowDesc) {
         this.rowDesc = rowDesc;
-        sumRow = new SingleRow<>(columnHeaders.size());
-        this.columnHeaders.addAll(columnHeaders);
+        sumRow = createRow(columnHeaders.size());
+        this.columnHeaders = new ArrayList<>(columnHeaders);
     }
 
     public final Map<String, Row<I>> getRows() {
diff --git a/rest/taskana-rest-spring/src/main/java/pro/taskana/rest/resource/ReportAssembler.java b/rest/taskana-rest-spring/src/main/java/pro/taskana/rest/resource/ReportAssembler.java
index 61a58c1b6..b8de8bcc9 100644
--- a/rest/taskana-rest-spring/src/main/java/pro/taskana/rest/resource/ReportAssembler.java
+++ b/rest/taskana-rest-spring/src/main/java/pro/taskana/rest/resource/ReportAssembler.java
@@ -66,15 +66,19 @@ public class ReportAssembler {
         return resource;
     }
 
-    private <I extends QueryItem, H extends ColumnHeader<? super I>> ReportResource toReportResource(
-        Report<I, H> report) {
+    <I extends QueryItem, H extends ColumnHeader<? super I>> ReportResource toReportResource(Report<I, H> report) {
+        return toReportResource(report, Instant.now());
+    }
+
+    <I extends QueryItem, H extends ColumnHeader<? super I>> ReportResource toReportResource(
+        Report<I, H> report, Instant time) {
         String[] header = report.getColumnHeaders()
             .stream()
             .map(ColumnHeader::getDisplayName)
             .toArray(String[]::new);
         ReportResource.MetaInformation meta = new ReportResource.MetaInformation(
             report.getClass().getSimpleName(),
-            Instant.now().toString(),
+            time.toString(),
             header,
             report.getRowDesc());
 
diff --git a/rest/taskana-rest-spring/src/test/java/pro/taskana/rest/resource/ReportResourceTest.java b/rest/taskana-rest-spring/src/test/java/pro/taskana/rest/resource/ReportResourceTest.java
new file mode 100644
index 000000000..0b3131728
--- /dev/null
+++ b/rest/taskana-rest-spring/src/test/java/pro/taskana/rest/resource/ReportResourceTest.java
@@ -0,0 +1,421 @@
+package pro.taskana.rest.resource;
+
+import static junit.framework.TestCase.assertTrue;
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+import java.time.ZoneOffset;
+import java.time.temporal.ChronoUnit;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.web.WebAppConfiguration;
+
+import pro.taskana.impl.report.header.TimeIntervalColumnHeader;
+import pro.taskana.impl.report.item.DetailedMonitorQueryItem;
+import pro.taskana.impl.report.item.MonitorQueryItem;
+import pro.taskana.report.ClassificationReport;
+import pro.taskana.report.WorkbasketReport;
+import pro.taskana.rest.TestConfiguration;
+
+/**
+ * Test for {@link ReportAssembler}.
+ */
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(classes = {TestConfiguration.class})
+@WebAppConfiguration
+public class ReportResourceTest {
+
+    @Autowired
+    private ReportAssembler reportAssembler;
+
+    private int daysDiff;
+    private LocalDateTime now;
+    private List<TimeIntervalColumnHeader> headers;
+
+    @Before
+    public void before() {
+        now = LocalDate.parse("2019-01-02").atStartOfDay();
+        daysDiff = (int) LocalDateTime.now().until(now, ChronoUnit.DAYS);
+        headers = IntStream.range(daysDiff - 5, daysDiff)
+            .mapToObj(TimeIntervalColumnHeader.Date::new)
+            .collect(Collectors.toList());
+
+    }
+
+    @Test
+    public void testEmptyReport() {
+        // given
+        WorkbasketReport report = new WorkbasketReport(headers);
+        // when
+        ReportResource resource = reportAssembler.toReportResource(report, now.toInstant(ZoneOffset.UTC));
+        // then
+
+        // meta
+        ReportResource.MetaInformation meta = resource.getMeta();
+        assertEquals("WorkbasketReport", meta.getName());
+        assertEquals("2019-01-02T00:00:00Z", meta.getDate());
+        assertEquals("WORKBASKET KEYS", meta.getRowDesc());
+        assertArrayEquals(headers.stream().map(TimeIntervalColumnHeader::getDisplayName).toArray(), meta.getHeader());
+        assertEquals("Total", meta.getTotalDesc());
+
+        // rows
+        assertTrue(resource.getRows().isEmpty());
+
+        // sumRow
+        assertEquals(ReportResource.SingleRowResource.class, resource.getSumRow().getClass());
+        assertEquals(0, resource.getSumRow().getTotal());
+        Map<String, Integer> cells = resource.getSumRow().getCells();
+        assertEquals(5, cells.size());
+        assertEquals(0, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+    }
+
+    @Test
+    public void testOneSingleRow() {
+        // given
+        ClassificationReport report = new ClassificationReport(headers);
+        MonitorQueryItem item = new MonitorQueryItem();
+        item.setAgeInDays(daysDiff - 1);
+        item.setNumberOfTasks(2);
+        item.setKey("key");
+        report.addItem(item);
+        // when
+        ReportResource resource = reportAssembler.toReportResource(report, now.toInstant(ZoneOffset.UTC));
+        // then
+
+        // meta
+        ReportResource.MetaInformation meta = resource.getMeta();
+        assertEquals("ClassificationReport", meta.getName());
+        assertEquals("2019-01-02T00:00:00Z", meta.getDate());
+        assertEquals("CLASSIFICATION KEYS", meta.getRowDesc());
+        assertArrayEquals(headers.stream().map(TimeIntervalColumnHeader::getDisplayName).toArray(), meta.getHeader());
+        assertEquals("Total", meta.getTotalDesc());
+
+        // rows
+        Map<String, ReportResource.RowResource> rows = resource.getRows();
+        assertEquals(1, rows.size());
+        ReportResource.RowResource row = rows.get("key");
+        assertEquals(ReportResource.SingleRowResource.class, row.getClass());
+        assertEquals(2, row.getTotal());
+        Map<String, Integer> cells = row.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(2, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+        // sumRow
+        ReportResource.RowResource sumRow = resource.getSumRow();
+        assertEquals(ReportResource.SingleRowResource.class, sumRow.getClass());
+        assertEquals(2, sumRow.getTotal());
+        cells = sumRow.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(2, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+    }
+
+    @Test
+    public void testMultipleSingleRows() {
+        // given
+        ClassificationReport report = new ClassificationReport(headers);
+        MonitorQueryItem item = new MonitorQueryItem();
+        item.setAgeInDays(daysDiff - 1);
+        item.setNumberOfTasks(2);
+        item.setKey("key");
+        report.addItem(item);
+        item.setKey("key2");
+        report.addItem(item);
+        // when
+        ReportResource resource = reportAssembler.toReportResource(report, now.toInstant(ZoneOffset.UTC));
+        // then
+
+        // meta
+        ReportResource.MetaInformation meta = resource.getMeta();
+        assertEquals("ClassificationReport", meta.getName());
+        assertEquals("2019-01-02T00:00:00Z", meta.getDate());
+        assertEquals("CLASSIFICATION KEYS", meta.getRowDesc());
+        assertArrayEquals(headers.stream().map(TimeIntervalColumnHeader::getDisplayName).toArray(), meta.getHeader());
+        assertEquals("Total", meta.getTotalDesc());
+
+        // rows
+        Map<String, ReportResource.RowResource> rows = resource.getRows();
+        assertEquals(2, rows.size());
+
+        ReportResource.RowResource row = rows.get("key");
+        assertEquals(ReportResource.SingleRowResource.class, row.getClass());
+        assertEquals(2, row.getTotal());
+        Map<String, Integer> cells = row.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(2, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+        row = rows.get("key2");
+        assertEquals(ReportResource.SingleRowResource.class, row.getClass());
+        assertEquals(2, row.getTotal());
+        cells = row.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(2, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+        // sumRow
+        ReportResource.RowResource sumRow = resource.getSumRow();
+        assertEquals(ReportResource.SingleRowResource.class, sumRow.getClass());
+        assertEquals(4, sumRow.getTotal());
+        cells = sumRow.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(4, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+    }
+
+    @Test
+    public void testOneFoldableRow() {
+        // given
+        ClassificationReport.DetailedClassificationReport report = new ClassificationReport.DetailedClassificationReport(
+            headers);
+        DetailedMonitorQueryItem item = new DetailedMonitorQueryItem();
+        item.setAgeInDays(daysDiff - 1);
+        item.setNumberOfTasks(2);
+        item.setKey("key");
+        item.setAttachmentKey("attachement");
+        report.addItem(item);
+        item.setAttachmentKey(null);
+        report.addItem(item);
+        // when
+        ReportResource resource = reportAssembler.toReportResource(report, now.toInstant(ZoneOffset.UTC));
+        // then
+
+        // meta
+        ReportResource.MetaInformation meta = resource.getMeta();
+        assertEquals("DetailedClassificationReport", meta.getName());
+        assertEquals("2019-01-02T00:00:00Z", meta.getDate());
+        assertEquals("TASK CLASSIFICATION KEYS", meta.getRowDesc());
+        assertArrayEquals(headers.stream().map(TimeIntervalColumnHeader::getDisplayName).toArray(), meta.getHeader());
+        assertEquals("Total", meta.getTotalDesc());
+
+        // rows
+        Map<String, ReportResource.RowResource> rows = resource.getRows();
+        assertEquals(1, rows.size());
+        assertEquals(ReportResource.FoldableRowResource.class, rows.get("key").getClass());
+        ReportResource.FoldableRowResource row = (ReportResource.FoldableRowResource) rows.get("key");
+        assertEquals(4, row.getTotal());
+        Map<String, Integer> cells = row.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(4, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+        assertEquals(2, row.getFoldableRows().size());
+        ReportResource.RowResource foldedRow = row.getFoldableRows().get("attachement");
+        assertEquals(ReportResource.SingleRowResource.class, foldedRow.getClass());
+        assertEquals(2, foldedRow.getTotal());
+        cells = foldedRow.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(2, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+        foldedRow = row.getFoldableRows().get("N/A");
+        assertEquals(ReportResource.SingleRowResource.class, foldedRow.getClass());
+        assertEquals(2, foldedRow.getTotal());
+        cells = foldedRow.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(2, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+        // sumRow
+        ReportResource.RowResource sumRow = resource.getSumRow();
+        assertEquals(ReportResource.FoldableRowResource.class, sumRow.getClass());
+        assertEquals(4, row.getTotal());
+        cells = row.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(4, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+        assertEquals(2, row.getFoldableRows().size());
+        foldedRow = row.getFoldableRows().get("attachement");
+        assertEquals(ReportResource.SingleRowResource.class, foldedRow.getClass());
+        assertEquals(2, foldedRow.getTotal());
+        cells = foldedRow.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(2, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+        foldedRow = row.getFoldableRows().get("N/A");
+        assertEquals(ReportResource.SingleRowResource.class, foldedRow.getClass());
+        assertEquals(2, foldedRow.getTotal());
+        cells = foldedRow.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(2, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+    }
+
+    @Test
+    public void testMultipleFoldableRows() {
+        // given
+        ClassificationReport.DetailedClassificationReport report = new ClassificationReport.DetailedClassificationReport(
+            headers);
+        DetailedMonitorQueryItem item = new DetailedMonitorQueryItem();
+        item.setAgeInDays(daysDiff - 1);
+        item.setNumberOfTasks(2);
+        item.setKey("key");
+        item.setAttachmentKey("attachement");
+        report.addItem(item);
+        item.setAttachmentKey(null);
+        report.addItem(item);
+        item.setKey("key2");
+        report.addItem(item);
+        // when
+        ReportResource resource = reportAssembler.toReportResource(report, now.toInstant(ZoneOffset.UTC));
+        // then
+
+        // meta
+        ReportResource.MetaInformation meta = resource.getMeta();
+        assertEquals("DetailedClassificationReport", meta.getName());
+        assertEquals("2019-01-02T00:00:00Z", meta.getDate());
+        assertEquals("TASK CLASSIFICATION KEYS", meta.getRowDesc());
+        assertArrayEquals(headers.stream().map(TimeIntervalColumnHeader::getDisplayName).toArray(), meta.getHeader());
+        assertEquals("Total", meta.getTotalDesc());
+
+        // rows
+        Map<String, ReportResource.RowResource> rows = resource.getRows();
+        assertEquals(2, rows.size());
+
+        assertEquals(ReportResource.FoldableRowResource.class, rows.get("key").getClass());
+        ReportResource.FoldableRowResource row = (ReportResource.FoldableRowResource) rows.get("key");
+        assertEquals(4, row.getTotal());
+        Map<String, Integer> cells = row.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(4, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+        assertEquals(2, row.getFoldableRows().size());
+        ReportResource.RowResource foldedRow = row.getFoldableRows().get("attachement");
+        assertEquals(ReportResource.SingleRowResource.class, foldedRow.getClass());
+        assertEquals(2, foldedRow.getTotal());
+        cells = foldedRow.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(2, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+        foldedRow = row.getFoldableRows().get("N/A");
+        assertEquals(ReportResource.SingleRowResource.class, foldedRow.getClass());
+        assertEquals(2, foldedRow.getTotal());
+        cells = foldedRow.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(2, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+        assertEquals(ReportResource.FoldableRowResource.class, rows.get("key2").getClass());
+        row = (ReportResource.FoldableRowResource) rows.get("key2");
+        assertEquals(2, row.getTotal());
+        cells = row.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(2, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+        assertEquals(1, row.getFoldableRows().size());
+        foldedRow = row.getFoldableRows().get("N/A");
+        assertEquals(ReportResource.SingleRowResource.class, foldedRow.getClass());
+        assertEquals(2, foldedRow.getTotal());
+        cells = foldedRow.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(2, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+        // sumRow
+        assertEquals(ReportResource.FoldableRowResource.class, resource.getSumRow().getClass());
+        ReportResource.FoldableRowResource sumRow = (ReportResource.FoldableRowResource) resource.getSumRow();
+        assertEquals(6, sumRow.getTotal());
+        cells = sumRow.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(6, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+        assertEquals(2, sumRow.getFoldableRows().size());
+        foldedRow = sumRow.getFoldableRows().get("attachement");
+        assertEquals(ReportResource.SingleRowResource.class, foldedRow.getClass());
+        assertEquals(2, foldedRow.getTotal());
+        cells = foldedRow.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(2, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+
+        foldedRow = sumRow.getFoldableRows().get("N/A");
+        assertEquals(ReportResource.SingleRowResource.class, foldedRow.getClass());
+        assertEquals(4, foldedRow.getTotal());
+        cells = foldedRow.getCells();
+        assertEquals(5, cells.size());
+        assertEquals(4, cells.get("2019-01-01").intValue());
+        assertEquals(0, cells.get("2018-12-31").intValue());
+        assertEquals(0, cells.get("2018-12-30").intValue());
+        assertEquals(0, cells.get("2018-12-29").intValue());
+        assertEquals(0, cells.get("2018-12-28").intValue());
+    }
+
+}