diff --git a/src/test/java/de/ids_mannheim/korap/collection/TestKrillCollectionJSON.java b/src/test/java/de/ids_mannheim/korap/collection/TestKrillCollectionJSON.java
index bb35479..41ce2dd 100644
--- a/src/test/java/de/ids_mannheim/korap/collection/TestKrillCollectionJSON.java
+++ b/src/test/java/de/ids_mannheim/korap/collection/TestKrillCollectionJSON.java
@@ -4,6 +4,12 @@
 import java.io.*;
 
 import de.ids_mannheim.korap.KrillCollection;
+import de.ids_mannheim.korap.Krill;
+import de.ids_mannheim.korap.KrillIndex;
+import de.ids_mannheim.korap.response.Result;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.JsonNode;
 
 import static de.ids_mannheim.korap.TestSimple.*;
 
@@ -72,6 +78,41 @@
     };
 
 
+    @Test
+    public void collectionMirror () throws Exception {
+        // Construct index
+        KrillIndex ki = new KrillIndex();
+        // Indexing test files
+        for (String i : new String[] { "00001", "00002", "00003", "00004",
+                "00005", "00006", "02439" }) {
+            ki.addDoc(
+                    getClass().getResourceAsStream("/wiki/" + i + ".json.gz"),
+                    true);
+        };
+        ki.commit();
+
+        Krill krill = new Krill(_getJSONString("collection_6.jsonld"));
+        Result kr = krill.apply(ki);
+        assertEquals(kr.getTotalResults(), 86);
+
+        ObjectMapper mapper = new ObjectMapper();
+        JsonNode res = mapper.readTree(kr.toJsonString());
+        assertTrue(res.at("/collection").isMissingNode());
+
+        krill = new Krill(_getJSONString("collection_6_withCollection.jsonld"));
+
+        kr = krill.apply(ki);
+        assertEquals(kr.getTotalResults(), 57);
+
+        res = mapper.readTree(kr.toJsonString());
+        assertFalse(res.at("/collection").isMissingNode());
+        assertEquals("koral:doc", res.at("/collection/@type").asText());
+        assertEquals("textClass", res.at("/collection/key").asText());
+        assertEquals("reisen", res.at("/collection/value").asText());
+        assertEquals("match:eq", res.at("/collection/match").asText());
+    };
+
+
     private String _getJSONString (String file) {
         return getString(getClass().getResource(path + file).getFile());
     };
diff --git a/src/test/java/de/ids_mannheim/korap/index/TestClassFilterIndex.java b/src/test/java/de/ids_mannheim/korap/index/TestClassFilterIndex.java
index 77ef45d..5a2565e 100644
--- a/src/test/java/de/ids_mannheim/korap/index/TestClassFilterIndex.java
+++ b/src/test/java/de/ids_mannheim/korap/index/TestClassFilterIndex.java
@@ -20,8 +20,9 @@
     private KrillIndex ki;
     private Result kr;
 
+
     @Test
-    public void testInclude() throws IOException {
+    public void testInclude () throws IOException {
         ki = new KrillIndex();
         ki.addDoc(TestReferenceIndex.createFieldDoc0());
         ki.commit();
@@ -36,8 +37,7 @@
         SpanClassFilterQuery sq = new SpanClassFilterQuery(sdq,
                 ClassOperation.INCLUDE, 2, 1, true);
 
-        assertEquals(
-                sq.toString(),
+        assertEquals(sq.toString(),
                 "spanClassFilter(spanDistance({1: <tokens:np />}, {2: <tokens:vp />}, "
                         + "[(w[0:1], notOrdered, notExcluded)]),INCLUDE,2,1)");
 
@@ -63,7 +63,8 @@
                 "Frankenstein, treat my daughter well. She [{2:is {1:the one that "
                         + "saved your master who you hold so dear}}].", kr
                         .getMatch(2).getSnippetBrackets());
-        assertEquals("Frankenstein, treat my daughter well. She [{2:is the one that "
+        assertEquals(
+                "Frankenstein, treat my daughter well. She [{2:is the one that "
                         + "saved {1:your master} who you hold so dear}].", kr
                         .getMatch(3).getSnippetBrackets());
         assertEquals(
@@ -72,8 +73,9 @@
 
     }
 
+
     @Test
-    public void testDisjoint() throws IOException {
+    public void testDisjoint () throws IOException {
         ki = new KrillIndex();
         ki.addDoc(TestReferenceIndex.createFieldDoc0());
         ki.commit();
@@ -94,7 +96,7 @@
 
         SpanClassFilterQuery sq = new SpanClassFilterQuery(sdq,
                 ClassOperation.DISJOINT, 2, 1, true);
-        
+
         kr = ki.search(sq, (short) 10);
         // for (Match km : kr.getMatches()) {
         // System.out.println(km.getStartPos() + "," + km.getEndPos()
@@ -119,10 +121,11 @@
                 kr.getMatch(2).getSnippetBrackets());
     }
 
+
     // Problem with SpanDistanceQuery - unordered distance spans,
     // -> unsorted
     @Test
-    public void testEqual() throws IOException {
+    public void testEqual () throws IOException {
         ki = new KrillIndex();
         ki.addDoc(TestReferenceIndex.createFieldDoc0());
         ki.commit();
@@ -155,8 +158,9 @@
 
     }
 
+
     @Test
-    public void testDiffer() throws IOException {
+    public void testDiffer () throws IOException {
         ki = new KrillIndex();
         ki.addDoc(TestReferenceIndex.createFieldDoc0());
         ki.commit();
@@ -194,7 +198,7 @@
 
 
     @Test
-    public void testIntersect() throws IOException {
+    public void testIntersect () throws IOException {
         ki = new KrillIndex();
         ki.addDoc(TestReferenceIndex.createFieldDoc0());
         ki.commit();
@@ -217,13 +221,14 @@
         SpanClassFilterQuery sq = new SpanClassFilterQuery(sdq3,
                 ClassOperation.INTERSECT, 1, 2, true);
 
-        assertEquals("spanClassFilter(spanDistance({1: spanDistance(<tokens:np />, " +
-        		"{3: <tokens:vb />}, [(w[0:1], notOrdered, notExcluded)])}, " +
-        		"{2: spanDistance(<tokens:prp />, <tokens:vb />, [(w[0:1], " +
-        		"notOrdered, notExcluded)])}, [(w[0:1], notOrdered, notExcluded)]),INTERSECT,1,2)",
+        assertEquals(
+                "spanClassFilter(spanDistance({1: spanDistance(<tokens:np />, "
+                        + "{3: <tokens:vb />}, [(w[0:1], notOrdered, notExcluded)])}, "
+                        + "{2: spanDistance(<tokens:prp />, <tokens:vb />, [(w[0:1], "
+                        + "notOrdered, notExcluded)])}, [(w[0:1], notOrdered, notExcluded)]),INTERSECT,1,2)",
                 sq.toString());
-        
-        
+
+
         kr = ki.search(sq, (short) 20);
 
         // for (Match km : kr.getMatches()) {
@@ -247,7 +252,7 @@
 
 
     @Test
-    public void testMultipleSameClasses() throws IOException {
+    public void testMultipleSameClasses () throws IOException {
 
         ki = new KrillIndex();
         ki.addDoc(TestReferenceIndex.createFieldDoc0());
@@ -269,10 +274,10 @@
 
         SpanClassFilterQuery sq = new SpanClassFilterQuery(sdq2,
                 ClassOperation.INCLUDE, 2, 1, true);
-        
+
         kr = ki.search(sdq2, (short) 20);
         assertEquals(6, kr.getTotalResults());
-        
+
         // for (Match km : kr.getMatches()) {
         // System.out.println(km.getStartPos() + "," + km.getEndPos()
         // + " "
diff --git a/src/test/java/de/ids_mannheim/korap/index/TestIndex.java b/src/test/java/de/ids_mannheim/korap/index/TestIndex.java
index be5fd8c..aac981e 100644
--- a/src/test/java/de/ids_mannheim/korap/index/TestIndex.java
+++ b/src/test/java/de/ids_mannheim/korap/index/TestIndex.java
@@ -75,6 +75,7 @@
 
     private Directory index = new RAMDirectory();
 
+
     @Test
     public void multiTerm () throws CorpusDataException {
         MultiTerm test = new MultiTerm("test");
@@ -110,6 +111,7 @@
         assertTrue(test.toString().startsWith("xip/l:\\#normal#0-5$"));
     };
 
+
     @Test
     public void multiTermToken () throws CorpusDataException {
         MultiTermToken test = new MultiTermToken("hunde", "pos:n", "m:gen:pl");
@@ -123,6 +125,7 @@
         assertEquals(test.terms.get(2).term, "m:gen:pl");
     };
 
+
     private List initIndexer () throws IOException {
         List<Map<String, String>> list = new ArrayList<>();
 
diff --git a/src/test/java/de/ids_mannheim/korap/index/TestReferenceIndex.java b/src/test/java/de/ids_mannheim/korap/index/TestReferenceIndex.java
index 4a56a04..f718ce3 100644
--- a/src/test/java/de/ids_mannheim/korap/index/TestReferenceIndex.java
+++ b/src/test/java/de/ids_mannheim/korap/index/TestReferenceIndex.java
@@ -28,6 +28,7 @@
     private KrillIndex ki;
     private Result kr;
 
+
     @Test
     public void testCase1 () throws IOException {
         ki = new KrillIndex();
@@ -55,7 +56,8 @@
         // SpanSegmentQuery ssq2 = new SpanSegmentQuery(sfq2, scq3,
         // true);
 
-        SpanRelationMatchQuery rq = new SpanRelationMatchQuery(srq, sfq1, scq3, true);
+        SpanRelationMatchQuery rq = new SpanRelationMatchQuery(srq, sfq1, scq3,
+                true);
 
         // System.out.println(rq.toString());
         SpanFocusQuery sfq3 = new SpanFocusQuery(rq, (byte) 1);
@@ -85,8 +87,9 @@
         assertEquals(7, kr.getMatch(0).getEndPos());
     }
 
+
     @Test
-    public void testCase2() throws IOException, QueryException {
+    public void testCase2 () throws IOException, QueryException {
 
         String filepath = getClass().getResource(
                 "/queries/reference/distance-reference.jsonld").getFile();
@@ -97,13 +100,12 @@
         // .{0,2} #3 & #3 -> #2
 
         assertEquals(
-            "spanReference(focus(#[1,2]spanSegment(focus(#2: "
-                    + "spanSegment(spanRelation(tokens:>:stanford/d:tag), "
-                    + "focus(3: spanDistance(focus(1: spanDistance({1: <tokens:vb />}, "
-                    + "{2: <tokens:prp />}, [(w[0:1], notOrdered, notExcluded)])), "
-                    + "{3: <tokens:nn />}, [(w[0:2], notOrdered, notExcluded)])))), "
-                    + "{2: <tokens:prp />})), 2)",
-            sq.toString());
+                "spanReference(focus(#[1,2]spanSegment(focus(#2: "
+                        + "spanSegment(spanRelation(tokens:>:stanford/d:tag), "
+                        + "focus(3: spanDistance(focus(1: spanDistance({1: <tokens:vb />}, "
+                        + "{2: <tokens:prp />}, [(w[0:1], notOrdered, notExcluded)])), "
+                        + "{3: <tokens:nn />}, [(w[0:2], notOrdered, notExcluded)])))), "
+                        + "{2: <tokens:prp />})), 2)", sq.toString());
 
         SpanElementQuery seq1 = new SpanElementQuery("tokens", "vb");
         // new SpanTermQuery(new Term("tokens", "c:vb"));
@@ -174,9 +176,10 @@
         // }
     }
 
+
     // multiple references
     @Test
-    public void testCase3() throws IOException, QueryException {
+    public void testCase3 () throws IOException, QueryException {
         ki = new KrillIndex();
         ki.addDoc(createFieldDoc0());
         ki.commit();
@@ -209,17 +212,17 @@
         assertEquals(13, kr.getMatch(1).getEndPos());
     }
 
+
     // multiple document
     @Test
-    public void testCase4() throws Exception {
+    public void testCase4 () throws Exception {
         ki = new KrillIndex();
         ki.addDoc(createFieldDoc0());
         ki.addDoc(createFieldDoc1());
         ki.commit();
 
         String filepath = getClass().getResource(
-                "/queries/reference/distance-reference.jsonld")
-                .getFile();
+                "/queries/reference/distance-reference.jsonld").getFile();
         SpanQueryWrapper sqwi = getJSONQuery(filepath);
         SpanQuery sq = sqwi.toQuery();
 
@@ -231,7 +234,8 @@
         assertEquals(4, kr.getMatch(3).getEndPos());
     }
 
-    public static FieldDocument createFieldDoc1() {
+
+    public static FieldDocument createFieldDoc1 () {
         FieldDocument fd = new FieldDocument();
         fd.addString("ID", "doc-1");
         fd.addTV(
@@ -256,69 +260,69 @@
         return fd;
     }
 
+
     public static FieldDocument createFieldDoc0 () {
         FieldDocument fd = new FieldDocument();
         fd.addString("ID", "doc-0");
         fd.addTV(
                 "tokens",
                 "Frankenstein, treat my daughter well. She is the one that saved your master who you hold so dear.",
-                
+
                 "[(0-12)s:Frankenstein|_0#0-12|<>:nn#0-12$<i>1<s>18|<>:s#0-37$<i>5<s>1|"
                         + "<>:np#0-13$<i>1<s>2|"
                         + "<:stanford/d:tag$<i>1<s>1<s>18<s>19]"
 
-                + "[(14-19)s:treat|_1#14-19|<>:vb#14-19$<i>2<s>19|<>:vp#14-36$<i>5<s>3|"
+                        + "[(14-19)s:treat|_1#14-19|<>:vb#14-19$<i>2<s>19|<>:vp#14-36$<i>5<s>3|"
                         + ">:stanford/d:tag$<i>0<s>2<s>19<s>18|"
                         + ">:stanford/d:tag$<i>3<s>3<s>19<s>21|"
                         + ">:stanford/d:tag$<i>4<s>4<s>19<s>22]"
 
-                + "[(20-22)s:my|_2#20-22|<>:prp#20-22$<i>3<s>20|<>:np#20-31$<i>4<s>4]"
+                        + "[(20-22)s:my|_2#20-22|<>:prp#20-22$<i>3<s>20|<>:np#20-31$<i>4<s>4]"
 
-                + "[(23-31)s:daughter|_3#23-31|<>:nn#23-31$<i>4<s>21|"
+                        + "[(23-31)s:daughter|_3#23-31|<>:nn#23-31$<i>4<s>21|"
                         + ">:stanford/d:tag$<i>2<s>5<s>21<s>20]"
 
-                + "[(32-36)s:well|_4#32-36|<>:rb#32-36$<i>5<s>22|<>:advp#32-36$<i>5<s>5]"
+                        + "[(32-36)s:well|_4#32-36|<>:rb#32-36$<i>5<s>22|<>:advp#32-36$<i>5<s>5]"
 
-                + "[(38-41)s:She|_5#38-41|<>:prp#38-41$<i>6<s>23|<>:np#38-41$<i>6<s>36|<>:s#38-97$<i>18<s>6]"
+                        + "[(38-41)s:She|_5#38-41|<>:prp#38-41$<i>6<s>23|<>:np#38-41$<i>6<s>36|<>:s#38-97$<i>18<s>6]"
 
-                + "[(42-44)s:is|_6#42-44|<>:vb#42-44$<i>7<s>24|<>:vp#42-96$<i>18<s>7]"
+                        + "[(42-44)s:is|_6#42-44|<>:vb#42-44$<i>7<s>24|<>:vp#42-96$<i>18<s>7]"
 
-                + "[(45-48)s:the|_7#45-48|<>:dt#45-48$<i>8<s>25|<>:np#45-52$<i>9<s>8|<>:np#45-96$<i>18<s>9]"
+                        + "[(45-48)s:the|_7#45-48|<>:dt#45-48$<i>8<s>25|<>:np#45-52$<i>9<s>8|<>:np#45-96$<i>18<s>9]"
 
-                + "[(49-52)s:one|_8#49-52|<>:nn#49-52$<i>9<s>26|"
+                        + "[(49-52)s:one|_8#49-52|<>:nn#49-52$<i>9<s>26|"
                         + ">:stanford/d:tag$<i>5<s>6<s>26<s>23|"
                         + ">:stanford/d:tag$<i>6<s>7<s>26<s>24|"
                         + ">:stanford/d:tag$<i>7<s>8<s>26<s>25|"
                         + ">:stanford/d:tag$<i>10<s>9<s>26<s>28]"
-                
-                + "[(53-57)s:that|_9#53-57|<>:rp#53-57$<i>10<s>27|<>:sb#53-96$<i>18<s>10]"
-                                              
-                + "[(58-63)s:saved|_10#58-63|<>:vb#58-63$<i>11<s>28|<>:s#58-96$<i>18<s>11|"
+
+                        + "[(53-57)s:that|_9#53-57|<>:rp#53-57$<i>10<s>27|<>:sb#53-96$<i>18<s>10]"
+
+                        + "[(58-63)s:saved|_10#58-63|<>:vb#58-63$<i>11<s>28|<>:s#58-96$<i>18<s>11|"
                         + "<>:vp#58-96$<i>18<s>12|"
                         + ">:stanford/d:tag$<i>9<s>10<s>28<s>27|"
                         + ">:stanford/d:tag$<i>12<s>11<s>28<s>30|"
                         + ">:stanford/d:tag$<i>15<s>12<s>28<s>33]"
 
-                + "[(64-68)s:your|_11#64-68|<>:prp#64-68$<i>12<s>29|<>:np#64-75$<i>13<s>13]"
+                        + "[(64-68)s:your|_11#64-68|<>:prp#64-68$<i>12<s>29|<>:np#64-75$<i>13<s>13]"
 
-                + "[(69-75)s:master|_12#69-75|<>:nn#69-75$<i>13<s>30|"
+                        + "[(69-75)s:master|_12#69-75|<>:nn#69-75$<i>13<s>30|"
                         + ">:stanford/d:tag$<i>11<s>13<s>30<s>29]"
 
-                + "[(76-79)s:who|_13#76-79|<>:rp#76-79$<i>14<s>31|<>:sb#76-96$<i>18<s>14]"
+                        + "[(76-79)s:who|_13#76-79|<>:rp#76-79$<i>14<s>31|<>:sb#76-96$<i>18<s>14]"
 
-                + "[(80-83)s:you|_14#80-83|<>:prp#80-83$<i>15<s>32|<>:np#80-83$<i>15<s>37|<>:s#80-96$<i>18<s>15]"
+                        + "[(80-83)s:you|_14#80-83|<>:prp#80-83$<i>15<s>32|<>:np#80-83$<i>15<s>37|<>:s#80-96$<i>18<s>15]"
 
-                + "[(84-88)s:hold|_15#84-88|<>:vb#84-88$<i>16<s>33|<>:vp#84-96$<i>18<s>16|"
+                        + "[(84-88)s:hold|_15#84-88|<>:vb#84-88$<i>16<s>33|<>:vp#84-96$<i>18<s>16|"
                         + ">:stanford/d:tag$<i>13<s>14<s>33<s>31|"
                         + ">:stanford/d:tag$<i>14<s>15<s>33<s>32|"
                         + ">:stanford/d:tag$<i>17<s>16<s>33<s>35]"
 
-                + "[(89-91)s:so|_16#89-91|<>:rb#89-91$<i>17<s>341|<>:adjp#89-96$<i>18<s>17]"
+                        + "[(89-91)s:so|_16#89-91|<>:rb#89-91$<i>17<s>341|<>:adjp#89-96$<i>18<s>17]"
 
-                + "[(92-96)s:dear|_17#92-96|<>:jj#92-96$<i>18<s>35|"
-                        + ">:stanford/d:tag$<i>16<s>17<s>35<s>34]"
-                 );
-                        
+                        + "[(92-96)s:dear|_17#92-96|<>:jj#92-96$<i>18<s>35|"
+                        + ">:stanford/d:tag$<i>16<s>17<s>35<s>34]");
+
         return fd;
     }
 }
diff --git a/src/test/java/de/ids_mannheim/korap/index/TestRelationIndex.java b/src/test/java/de/ids_mannheim/korap/index/TestRelationIndex.java
index 63d2a64..8618592 100644
--- a/src/test/java/de/ids_mannheim/korap/index/TestRelationIndex.java
+++ b/src/test/java/de/ids_mannheim/korap/index/TestRelationIndex.java
@@ -289,6 +289,7 @@
         assertEquals(4, kr.getMatch(5).getEndPos());
     }
 
+
     /**
      * Relations only with/out attribute
      * */
@@ -307,9 +308,8 @@
 
         // child-of with attr func=sbj
         SpanWithAttributeQuery wq = new SpanWithAttributeQuery(fq,
-                new SpanAttributeQuery(
-                        new SpanTermQuery(new Term("base", "r@:func=sbj")),
-                        true), true);
+                new SpanAttributeQuery(new SpanTermQuery(new Term("base",
+                        "r@:func=sbj")), true), true);
 
         kr = ki.search(wq, (short) 20);
         assertEquals((long) 1, kr.getTotalResults());
@@ -385,11 +385,12 @@
         assertEquals(7, kr.getMatch(6).getEndPos());
     }
 
+
     /**
      * Dependency relations with attribute
      * */
     @Test
-    public void testCase5() throws IOException {
+    public void testCase5 () throws IOException {
         ki.addDoc(createFieldDoc2());
         ki.commit();
 
@@ -430,6 +431,7 @@
 
     }
 
+
     /**
      * Relation with specific sources, return any targets
      * */
@@ -485,11 +487,11 @@
         ki.commit();
 
         //return source of dep relations to pos:NN
-        
+
         SpanTermWithIdQuery tq = new SpanTermWithIdQuery(new Term("base",
                 "pos:NN"), true);
-        SpanRelationQuery srq = new SpanRelationQuery(new SpanTermQuery(new Term("base",
-                "<:dep")), true);
+        SpanRelationQuery srq = new SpanRelationQuery(new SpanTermQuery(
+                new Term("base", "<:dep")), true);
         srq.setSourceClass((byte) 1);
         SpanRelationMatchQuery rm = new SpanRelationMatchQuery(srq, tq, true);
         SpanQuery rv = new SpanFocusQuery(rm, (byte) 1);
@@ -505,8 +507,7 @@
 
         // return target of dep relations from pos:NN
         srq = new SpanRelationQuery(
-                new SpanTermQuery(
-                new Term("base", ">:dep")), true);
+                new SpanTermQuery(new Term("base", ">:dep")), true);
         srq.setTargetClass((byte) 1);
         rm = new SpanRelationMatchQuery(srq, tq, true);
         rv = new SpanFocusQuery(rm, (byte) 1);
@@ -525,7 +526,8 @@
 
     /**
      * Relation with specific sources and return any targets <br/>
-     * Relation with specific sources and targets, return the targets <br/>
+     * Relation with specific sources and targets, return the targets
+     * <br/>
      * Relation with specific sources and targets, return the sources
      * 
      * @throws IOException
@@ -606,8 +608,9 @@
 
     }
 
+
     @Test
-    public void testCase10() throws IOException {
+    public void testCase10 () throws IOException {
         ki.addDoc(createFieldDoc2());
         ki.commit();
         SpanElementQuery seq1 = new SpanElementQuery("base", "np");
diff --git a/src/test/java/de/ids_mannheim/korap/query/TestKrillQueryJSON.java b/src/test/java/de/ids_mannheim/korap/query/TestKrillQueryJSON.java
index c0e1cf5..df00673 100644
--- a/src/test/java/de/ids_mannheim/korap/query/TestKrillQueryJSON.java
+++ b/src/test/java/de/ids_mannheim/korap/query/TestKrillQueryJSON.java
@@ -245,6 +245,7 @@
         assertEquals(sqwi.toQuery().toString(), "tokens:base/p:foo");
     };
 
+
     @Test
     public void queryJSONBspClass () throws QueryException {
         SpanQueryWrapper sqwi = jsonQuery(getClass().getResource(
@@ -450,46 +451,40 @@
                 "spanOverlap(<tokens:s />, spanNext(tokens:tt/p:CARD, SpanMultiTermQueryWrapper(tokens:/tt/p:N.*/)))");
     };
 
+
     @Test
     public void queryJSONflags1 () throws QueryException {
         // buchstabe/i
         SpanQueryWrapper sqwi = jsonQuery(getClass().getResource(
                 "/queries/flags/caseInsensitive.jsonld").getFile());
 
-        assertEquals(
-                sqwi.toQuery().toString(),
-                "tokens:i:buchstabe");
+        assertEquals(sqwi.toQuery().toString(), "tokens:i:buchstabe");
     };
 
+
     @Test
     public void queryJSONflags2 () throws QueryException {
         // buchstabe/i
         try {
-            String json = getString(
-                getClass().getResource(
-                    "/queries/flags/unknown1.jsonld"
-                ).getFile()
-            );
+            String json = getString(getClass().getResource(
+                    "/queries/flags/unknown1.jsonld").getFile());
             KrillQuery kq = new KrillQuery("tokens");
-            assertEquals(kq.fromJson(json).toQuery().toString(),"tokens:s:buchstabe");
-            assertEquals(kq.getWarning(0).getCode(), 748);
-            
-            json = getString(
-                getClass().getResource(
-                    "/queries/flags/unknown2.jsonld"
-                ).getFile()
-            );
-            kq = new KrillQuery("tokens");
-            assertEquals(kq.fromJson(json).toQuery().toString(),"tokens:i:buchstabe");
+            assertEquals(kq.fromJson(json).toQuery().toString(),
+                    "tokens:s:buchstabe");
             assertEquals(kq.getWarning(0).getCode(), 748);
 
-            json = getString(
-                getClass().getResource(
-                    "/queries/flags/unknown3.jsonld"
-                ).getFile()
-            );
+            json = getString(getClass().getResource(
+                    "/queries/flags/unknown2.jsonld").getFile());
             kq = new KrillQuery("tokens");
-            assertEquals(kq.fromJson(json).toQuery().toString(),"tokens:i:buchstabe");
+            assertEquals(kq.fromJson(json).toQuery().toString(),
+                    "tokens:i:buchstabe");
+            assertEquals(kq.getWarning(0).getCode(), 748);
+
+            json = getString(getClass().getResource(
+                    "/queries/flags/unknown3.jsonld").getFile());
+            kq = new KrillQuery("tokens");
+            assertEquals(kq.fromJson(json).toQuery().toString(),
+                    "tokens:i:buchstabe");
             assertEquals(kq.getWarning(0).getCode(), 748);
 
         }
@@ -498,6 +493,7 @@
         };
     };
 
+
     public static String getString (String path) {
         StringBuilder contentBuilder = new StringBuilder();
         try {
diff --git a/src/test/java/de/ids_mannheim/korap/query/TestSpanReferenceQueryJSON.java b/src/test/java/de/ids_mannheim/korap/query/TestSpanReferenceQueryJSON.java
index 57c29bc..a401916 100644
--- a/src/test/java/de/ids_mannheim/korap/query/TestSpanReferenceQueryJSON.java
+++ b/src/test/java/de/ids_mannheim/korap/query/TestSpanReferenceQueryJSON.java
@@ -14,7 +14,7 @@
 public class TestSpanReferenceQueryJSON {
 
     @Test
-    public void testFirstOperandRef() throws IOException, QueryException {
+    public void testFirstOperandRef () throws IOException, QueryException {
 
         String filepath = getClass().getResource(
                 "/queries/reference/first-operand-reference.jsonld").getFile();
@@ -30,8 +30,9 @@
                 sq.toString());
     }
 
+
     @Test
-    public void testSecondOperandRef() throws QueryException {
+    public void testSecondOperandRef () throws QueryException {
 
         String filepath = getClass().getResource(
                 "/queries/reference/second-operand-reference.jsonld").getFile();
@@ -47,8 +48,9 @@
                         + "{3: tokens:p:P}), 3)", sq.toString());
     }
 
+
     @Test
-    public void testMultipleReferences() throws QueryException {
+    public void testMultipleReferences () throws QueryException {
         String filepath = getClass().getResource(
                 "/queries/reference/multiple-references.jsonld").getFile();
         SpanQueryWrapper sqwi = getJSONQuery(filepath);
@@ -60,55 +62,38 @@
                 "spanReference(focus(#[1,2]spanSegment(focus(#2: spanSegment(spanRelation(tokens:>:mate/d:HEAD), "
                         + "focus(2: spanReference(spanNext(focus(1: spanNext(focus(2: spanNext({1: <tokens:c:VP />}, "
                         + "{2: <tokens:c:NP />})), {3: <tokens:c:PP />})), {3: <tokens:c:PP />}), 3)))), "
-                        + "{1: <tokens:c:VP />})), 1)",
-                sq.toString());
+                        + "{1: <tokens:c:VP />})), 1)", sq.toString());
     }
 
+
     @Test
-    public void testDistanceReferences() throws QueryException {
+    public void testDistanceReferences () throws QueryException {
         String filepath = getClass().getResource(
-            "/queries/reference/bug-multiple-distance-simple.jsonld"
-        ).getFile();
+                "/queries/reference/bug-multiple-distance-simple.jsonld")
+                .getFile();
         SpanQueryWrapper sqwi = getJSONQuery(filepath);
         SpanQuery sq = sqwi.toQuery();
 
-        assertEquals("spanDistance(<tokens:c:vb />, <tokens:c:prp />, [(w[1:1], notOrdered, notExcluded)])", sq.toString());
+        assertEquals(
+                "spanDistance(<tokens:c:vb />, <tokens:c:prp />, [(w[1:1], notOrdered, notExcluded)])",
+                sq.toString());
 
         // "/queries/reference/distance-reference.jsonld").getFile();
         filepath = getClass().getResource(
-            "/queries/reference/bug-multiple-distance.jsonld"
-        ).getFile();
+                "/queries/reference/bug-multiple-distance.jsonld").getFile();
         sqwi = getJSONQuery(filepath);
         sq = sqwi.toQuery();
 
         // 'cat="VP" & cat="NP" & cat="PP" & #1 . #2 & #2 . #3 & #1 .
         // #3 & #2 ->dep #1'
-        assertEquals(
-        "spanReference("+
-          "focus("+
-            "#[1,2]spanSegment("+
-              "focus("+
-                "#2: spanSegment("+
-                  "spanRelation(tokens:>:stanford/d:tag), " +
-                    "focus("+
-                      "2: spanDistance("+
-                        "focus("+
-                          "1: spanDistance("+
-                            "<tokens:c:vb />, "+
-                            "{1: <tokens:c:prp />}, " +
-                            "[(w[1:1], notOrdered, notExcluded)]"+
-                          ")"+
-                        "), "+
-                        "{2: <tokens:c:nn />}, "+
-                        "[(w[0:2], ordered, notExcluded)]"+
-                      ")"+
-                    ")"+
-                  ")"+
-                "), " +
-                "{1: <tokens:c:prp />}"+
-              ")"+
-            "), 1"+
-          ")",
-        sq.toString());
+        assertEquals("spanReference(" + "focus(" + "#[1,2]spanSegment("
+                + "focus(" + "#2: spanSegment("
+                + "spanRelation(tokens:>:stanford/d:tag), " + "focus("
+                + "2: spanDistance(" + "focus(" + "1: spanDistance("
+                + "<tokens:c:vb />, " + "{1: <tokens:c:prp />}, "
+                + "[(w[1:1], notOrdered, notExcluded)]" + ")" + "), "
+                + "{2: <tokens:c:nn />}, " + "[(w[0:2], ordered, notExcluded)]"
+                + ")" + ")" + ")" + "), " + "{1: <tokens:c:prp />}" + ")"
+                + "), 1" + ")", sq.toString());
     }
 }
diff --git a/src/test/java/de/ids_mannheim/korap/query/TestSpanRelationQueryJSON.java b/src/test/java/de/ids_mannheim/korap/query/TestSpanRelationQueryJSON.java
index fccd34a..b051509 100644
--- a/src/test/java/de/ids_mannheim/korap/query/TestSpanRelationQueryJSON.java
+++ b/src/test/java/de/ids_mannheim/korap/query/TestSpanRelationQueryJSON.java
@@ -89,6 +89,7 @@
                 sq.toString());
     }
 
+
     @Test
     public void testFocusSource () throws QueryException {
         //
@@ -101,8 +102,9 @@
                 sq.toString());
     }
 
+
     @Test
-    public void testFocusTarget() throws QueryException {
+    public void testFocusTarget () throws QueryException {
         String filepath = getClass().getResource(
                 "/queries/relation/focus-target.json").getFile();
         SpanQueryWrapper sqwi = getJSONQuery(filepath);
@@ -113,8 +115,9 @@
                 sq.toString());
     }
 
+
     @Test
-    public void testFocusEmptyTarget() throws QueryException {
+    public void testFocusEmptyTarget () throws QueryException {
         String filepath = getClass().getResource(
                 "/queries/relation/focus-empty-target.json").getFile();
         SpanQueryWrapper sqwi = getJSONQuery(filepath);
@@ -124,8 +127,9 @@
                 sq.toString());
     }
 
+
     @Test
-    public void testFocusEmptyBoth() throws QueryException {
+    public void testFocusEmptyBoth () throws QueryException {
         String filepath = getClass().getResource(
                 "/queries/relation/focus-empty-both.json").getFile();
         SpanQueryWrapper sqwi = getJSONQuery(filepath);
diff --git a/src/test/java/de/ids_mannheim/korap/response/TestResponse.java b/src/test/java/de/ids_mannheim/korap/response/TestResponse.java
index 423af96..b93ddfb 100644
--- a/src/test/java/de/ids_mannheim/korap/response/TestResponse.java
+++ b/src/test/java/de/ids_mannheim/korap/response/TestResponse.java
@@ -84,6 +84,7 @@
         assertEquals("Fehler 4", respJson.at("/errors/0/1").asText());
     };
 
+
     // TODO: Skip this for the moment and refactor later
     @Ignore
     public void testResponseDeserialzation () throws IOException {
diff --git a/src/test/java/de/ids_mannheim/korap/search/TestKrill.java b/src/test/java/de/ids_mannheim/korap/search/TestKrill.java
index 8c4cd40..fd2e7c3 100644
--- a/src/test/java/de/ids_mannheim/korap/search/TestKrill.java
+++ b/src/test/java/de/ids_mannheim/korap/search/TestKrill.java
@@ -188,10 +188,12 @@
         assertEquals(kr.getTotalResults(), 1);
     };
 
+
     // Todo: There SHOULD be a failure here, but Koral currently creates empty collections
     @Test
     public void queryJSONapiTest1 () {
-        Krill test = new Krill("{\"@context\":\"http://korap.ids-mannheim.de/ns/koral/0.3/context.jsonld\",\"errors\":[],\"warnings\":[],\"messages\":[],\"collection\":{},\"query\":{\"@type\":\"koral:token\",\"wrap\":{\"@type\":\"koral:term\",\"layer\":\"orth\",\"key\":\"Baum\",\"match\":\"match:eq\"}},\"meta\":{}}");
+        Krill test = new Krill(
+                "{\"@context\":\"http://korap.ids-mannheim.de/ns/koral/0.3/context.jsonld\",\"errors\":[],\"warnings\":[],\"messages\":[],\"collection\":{},\"query\":{\"@type\":\"koral:token\",\"wrap\":{\"@type\":\"koral:term\",\"layer\":\"orth\",\"key\":\"Baum\",\"match\":\"match:eq\"}},\"meta\":{}}");
         assertFalse(test.hasErrors());
     };
 
diff --git a/src/test/java/de/ids_mannheim/korap/search/TestResult.java b/src/test/java/de/ids_mannheim/korap/search/TestResult.java
index 7425cfd..6d9a4d5 100644
--- a/src/test/java/de/ids_mannheim/korap/search/TestResult.java
+++ b/src/test/java/de/ids_mannheim/korap/search/TestResult.java
@@ -149,13 +149,13 @@
         Krill ks = new Krill(json);
         Result kr = ks.apply(ki);
         assertEquals((long) 7, kr.getTotalResults());
-        
+
         ObjectMapper mapper = new ObjectMapper();
         JsonNode res = mapper.readTree(kr.toJsonString());
 
         assertEquals(7, res.at("/meta/totalResults").asInt());
-        assertEquals("spanOr([tokens:s:a, tokens:s:b])", res.at("/meta/serialQuery")
-                .asText());
+        assertEquals("spanOr([tokens:s:a, tokens:s:b])",
+                res.at("/meta/serialQuery").asText());
         assertEquals(5, res.at("/meta/itemsPerPage").asInt());
         assertEquals(0, res.at("/meta/startIndex").asInt());
 
@@ -175,24 +175,19 @@
 
         // Query
         assertEquals("koral:group", res.at("/query/@type").asText());
-        assertEquals("operation:or", res.at("/query/operation")
-                .asText());
+        assertEquals("operation:or", res.at("/query/operation").asText());
 
-        assertEquals("koral:token", res.at("/query/operands/0/@type")
+        assertEquals("koral:token", res.at("/query/operands/0/@type").asText());
+        assertEquals("koral:term", res.at("/query/operands/0/wrap/@type")
                 .asText());
-        assertEquals("koral:term",
-                res.at("/query/operands/0/wrap/@type").asText());
-        assertEquals("orth", res.at("/query/operands/0/wrap/layer")
-                .asText());
+        assertEquals("orth", res.at("/query/operands/0/wrap/layer").asText());
         assertEquals("a", res.at("/query/operands/0/wrap/key").asText());
         assertEquals("match:eq", res.at("/query/operands/0/wrap/match")
                 .asText());
-        assertEquals("koral:token", res.at("/query/operands/1/@type")
+        assertEquals("koral:token", res.at("/query/operands/1/@type").asText());
+        assertEquals("koral:term", res.at("/query/operands/1/wrap/@type")
                 .asText());
-        assertEquals("koral:term",
-                res.at("/query/operands/1/wrap/@type").asText());
-        assertEquals("orth", res.at("/query/operands/1/wrap/layer")
-                .asText());
+        assertEquals("orth", res.at("/query/operands/1/wrap/layer").asText());
         assertEquals("b", res.at("/query/operands/1/wrap/key").asText());
         assertEquals("match:eq", res.at("/query/operands/1/wrap/match")
                 .asText());
@@ -240,8 +235,8 @@
         JsonNode res = mapper.readTree(kr.toTokenListJsonString());
 
         assertEquals(3, res.at("/meta/totalResults").asInt());
-        assertEquals("spanNext(base:s:a, base:s:b)", res.at("/meta/serialQuery")
-                .asText());
+        assertEquals("spanNext(base:s:a, base:s:b)", res
+                .at("/meta/serialQuery").asText());
         assertEquals(0, res.at("/meta/startIndex").asInt());
         assertEquals(25, res.at("/meta/itemsPerPage").asInt());
 
diff --git a/src/test/resources/queries/collections/collection_6.jsonld b/src/test/resources/queries/collections/collection_6.jsonld
new file mode 100644
index 0000000..5e60008
--- /dev/null
+++ b/src/test/resources/queries/collections/collection_6.jsonld
@@ -0,0 +1,19 @@
+{
+  "@context":"http://korap.ids-mannheim.de/ns/koral/0.3/context.jsonld",
+  "errors":[],
+  "warnings":[],
+  "messages":[],
+  "query":{
+    "@type":"koral:token",
+    "wrap":{
+      "@type":"koral:term",
+      "layer":"orth",
+      "key":"der",
+      "match":"match:eq",
+      "foundry":"opennlp"
+    }
+  },
+  "meta":{
+    "cutOff":null
+  }
+}
diff --git a/src/test/resources/queries/collections/collection_6_withCollection.jsonld b/src/test/resources/queries/collections/collection_6_withCollection.jsonld
new file mode 100644
index 0000000..91d960a
--- /dev/null
+++ b/src/test/resources/queries/collections/collection_6_withCollection.jsonld
@@ -0,0 +1,25 @@
+{
+  "@context":"http://korap.ids-mannheim.de/ns/koral/0.3/context.jsonld",
+  "errors":[],
+  "warnings":[],
+  "messages":[],
+  "collection":{
+    "@type":"koral:doc",
+    "key":"textClass",
+    "value":"reisen",
+    "match":"match:eq"
+  },
+  "query":{
+    "@type":"koral:token",
+    "wrap":{
+      "@type":"koral:term",
+      "layer":"orth",
+      "key":"der",
+      "match":"match:eq",
+      "foundry":"opennlp"
+    }
+  },
+  "meta":{
+    "cutOff":null
+  }
+}