diff --git a/example/lib/main.dart b/example/lib/main.dart
index 34cdb4c..b0255c8 100644
--- a/example/lib/main.dart
+++ b/example/lib/main.dart
@@ -54,6 +54,12 @@ class _TimetableDemoState extends State<TimetableDemo> {
       child: Text('High Tea'),
       id: 10,
     ),
+    TimeBlock(
+      start: TimeOfDay(hour: 18, minute: 0),
+      end: TimeOfDay(hour: 18, minute: 15),
+      child: Text('High Tea'),
+      id: 0,
+    ),
   ];
 
   final List<TimeBlock> groupedBlocks = [
@@ -102,6 +108,12 @@ class _TimetableDemoState extends State<TimetableDemo> {
       child: Text('High Tea'),
       id: 10,
     ),
+    TimeBlock(
+      start: TimeOfDay(hour: 18, minute: 0),
+      end: TimeOfDay(hour: 18, minute: 15),
+      child: Text('High Tea'),
+      id: 0,
+    ),
   ];
 
   @override
diff --git a/lib/src/block_service.dart b/lib/src/block_service.dart
new file mode 100644
index 0000000..37131f0
--- /dev/null
+++ b/lib/src/block_service.dart
@@ -0,0 +1,115 @@
+part of timetable;
+
+/// Combine blocks that have the same id and the same time.
+List<TimeBlock> collapseBlocks(List<TimeBlock> blocks) {
+  var newBlocks = <TimeBlock>[];
+  var groupedBlocks = <List<TimeBlock>>[];
+  // order blocks by id and collides with another block
+  for (var block in blocks) {
+    // check if the block is already in one of the grouped blocks
+    var found = false;
+    if (block.id == 0) {
+      newBlocks.add(block);
+      continue;
+    }
+    for (var groupedBlock in groupedBlocks) {
+      if (groupedBlock.first.id == block.id &&
+          groupedBlock.first.start == block.start &&
+          groupedBlock.first.end == block.end) {
+        groupedBlock.add(block);
+        found = true;
+        break;
+      }
+    }
+    if (!found) {
+      if (blocks
+          .where(
+            (b) =>
+                b != block &&
+                b.id == block.id &&
+                b.start == block.start &&
+                b.end == block.end,
+          )
+          .isNotEmpty) {
+        groupedBlocks.add([block]);
+      } else {
+        newBlocks.add(block);
+      }
+    }
+  }
+
+  for (var block in groupedBlocks) {
+    // combine the blocks into one block
+    // calculate the endtime of the combined block
+    var startMinute = block.first.start.minute + block.first.start.hour * 60;
+    var endMinute = block.first.end.minute + block.first.end.hour * 60;
+    var durationMinute = (endMinute - startMinute) * block.length;
+
+    var endTime = TimeOfDay(
+      hour: (startMinute + durationMinute) ~/ 60,
+      minute: (startMinute + durationMinute) % 60,
+    );
+    var newBlock = TimeBlock(
+      start: block.first.start,
+      end: endTime,
+      id: block.first.id,
+      child: Column(
+        children: [
+          for (var b in block) ...[b.child ?? Container()],
+        ],
+      ),
+    );
+    newBlocks.add(newBlock);
+  }
+  return newBlocks;
+}
+
+/// Group blocks with the same id together.
+/// Items in the same group will be displayed in the same column.
+List<List<TimeBlock>> groupBlocksById(List<TimeBlock> blocks) {
+  var groupedBlocks = <List<TimeBlock>>[];
+  var defaultGroup = <TimeBlock>[];
+  for (var block in blocks) {
+    var found = false;
+    if (block.id == 0) {
+      defaultGroup.add(block);
+    } else {
+      for (var groupedBlock in groupedBlocks) {
+        if (groupedBlock.first.id == block.id) {
+          groupedBlock.add(block);
+          found = true;
+          break;
+        }
+      }
+      if (!found) {
+        groupedBlocks.add([block]);
+      }
+    }
+  }
+  for (var block in defaultGroup) {
+    groupedBlocks.add([block]);
+  }
+  return groupedBlocks;
+}
+
+/// Nerge blocks that fit below eachother into one column.
+List<List<TimeBlock>> mergeBlocksInColumns(List<TimeBlock> blocks) {
+  var mergedBlocks = <List<TimeBlock>>[];
+  // try to put blocks in the same column if the time doesn´t collide
+  for (var block in blocks) {
+    var mergeIndex = 0;
+
+    for (var mergedBlock in mergedBlocks) {
+      if (!mergedBlock.any((b) => b.collidesWith(block))) {
+        mergedBlock.add(block);
+        break;
+      } else {
+        mergeIndex++;
+      }
+    }
+    if (mergedBlocks.length == mergeIndex) {
+      mergedBlocks.add([block]);
+    }
+  }
+  return mergedBlocks;
+}
diff --git a/lib/src/timetable.dart b/lib/src/timetable.dart
index ce4f535..a161b30 100644
--- a/lib/src/timetable.dart
+++ b/lib/src/timetable.dart
@@ -14,7 +14,7 @@ class Timetable extends StatefulWidget {
     this.tablePaddingEnd = 15,
     this.theme = const TableTheme(),
     this.mergeBlocks = false,
-    this.collapseBlocks = false,
+    this.collapseBlocks = true,
     Key? key,
   }) : super(key: key);
 
@@ -55,6 +55,7 @@ class Timetable extends StatefulWidget {
   final bool mergeBlocks;
 
   /// Whether or not to collapse blocks in 1 column if they have the same id.
+  /// If blocks have the same id and time they will be combined into one block.
   final bool collapseBlocks;
 
   @override
@@ -81,7 +82,12 @@ class _TimetableState extends State<Timetable> {
 
   @override
   Widget build(BuildContext context) {
-    var blocks = _collapseBlocks(widget.timeBlocks);
+    List<TimeBlock> blocks;
+    if (widget.collapseBlocks) {
+      blocks = collapseBlocks(widget.timeBlocks);
+    } else {
+      blocks = widget.timeBlocks;
+    }
     return SingleChildScrollView(
       physics: widget.scrollPhysics ?? const BouncingScrollPhysics(),
       controller: _scrollController,
@@ -106,54 +112,21 @@ class _TimetableState extends State<Timetable> {
                 child: Row(
                   crossAxisAlignment: CrossAxisAlignment.start,
                   children: [
-                    if (!widget.mergeBlocks && !widget.collapseBlocks) ...[
+                    if (widget.mergeBlocks || widget.collapseBlocks) ...[
+                      for (var orderedBlocks in (widget.mergeBlocks)
+                          ? mergeBlocksInColumns(blocks)
+                          : groupBlocksById(blocks)) ...[
+                        Stack(
+                          children: [
+                            for (var block in orderedBlocks) ...[
+                              _showBlock(block),
+                            ],
+                          ],
+                        ),
+                      ],
+                    ] else ...[
                       for (var block in blocks) ...[
-                        Block(
-                          start: block.start,
-                          end: block.end,
-                          startHour: widget.startHour,
-                          hourHeight: widget.hourHeight,
-                          blockWidth: widget.blockWidth,
-                          blockColor: widget.blockColor,
-                          child: block.child,
-                        ),
-                      ],
-                    ] else if (widget.mergeBlocks) ...[
-                      for (var mergedBlocks
-                          in _mergeBlocksInColumns(blocks)) ...[
-                        Stack(
-                          children: [
-                            for (var block in mergedBlocks) ...[
-                              Block(
-                                start: block.start,
-                                end: block.end,
-                                startHour: widget.startHour,
-                                hourHeight: widget.hourHeight,
-                                blockWidth: widget.blockWidth,
-                                blockColor: widget.blockColor,
-                                child: block.child,
-                              ),
-                            ],
-                          ],
-                        ),
-                      ],
-                    ] else if (widget.collapseBlocks) ...[
-                      for (var groupedBlocks in _groupBlocksById(blocks)) ...[
-                        Stack(
-                          children: [
-                            for (var block in groupedBlocks) ...[
-                              Block(
-                                start: block.start,
-                                end: block.end,
-                                startHour: widget.startHour,
-                                hourHeight: widget.hourHeight,
-                                blockWidth: widget.blockWidth,
-                                blockColor: widget.blockColor,
-                                child: block.child,
-                              ),
-                            ],
-                          ],
-                        ),
+                        _showBlock(block),
                       ],
                     ],
                     SizedBox(
@@ -171,111 +144,16 @@ class _TimetableState extends State<Timetable> {
     );
   }
 
-  /// Copmbine blocks that have the same id and the same time.
-  List<TimeBlock> _collapseBlocks(List<TimeBlock> blocks) {
-    var newBlocks = <TimeBlock>[];
-    var groupedBlocks = <List<TimeBlock>>[];
-    // order blocks by id and collides with another block
-    for (var block in blocks) {
-      // check if the block is already in one of the grouped blocks
-      var found = false;
-      for (var groupedBlock in groupedBlocks) {
-        if (groupedBlock.first.id == block.id &&
-            groupedBlock.first.start == block.start &&
-            groupedBlock.first.end == block.end) {
-          groupedBlock.add(block);
-          found = true;
-          break;
-        }
-      }
-      if (!found) {
-        if (blocks
-            .where(
-              (b) =>
-                  b != block &&
-                  b.id == block.id &&
-                  b.start == block.start &&
-                  b.end == block.end,
-            )
-            .isNotEmpty) {
-          groupedBlocks.add([block]);
-        } else {
-          newBlocks.add(block);
-        }
-      }
-    }
-    // 8.10 8.40 8.55
-    //
-    for (var block in groupedBlocks) {
-      // combine the blocks into one block
-      // calculate the endtime of the combined block
-      var startMinute = block.first.start.minute + block.first.start.hour * 60;
-      var endMinute = block.first.end.minute + block.first.end.hour * 60;
-      var durationMinute = (endMinute - startMinute) * block.length;
-
-      var endTime = TimeOfDay(
-        hour: (startMinute + durationMinute) ~/ 60,
-        minute: (startMinute + durationMinute) % 60,
-      );
-      var newBlock = TimeBlock(
-        start: block.first.start,
-        end: endTime,
-        child: Column(
-          children: [
-            for (var b in block) ...[b.child ?? Container()],
-          ],
-        ),
-      );
-      newBlocks.add(newBlock);
-    }
-    return newBlocks;
-  }
-
-  List<List<TimeBlock>> _groupBlocksById(List<TimeBlock> blocks) {
-    var groupedBlocks = <List<TimeBlock>>[];
-    var defaultGroup = <TimeBlock>[];
-    for (var block in blocks) {
-      var found = false;
-      if (block.id == 0) {
-        defaultGroup.add(block);
-      } else {
-        for (var groupedBlock in groupedBlocks) {
-          if (groupedBlock.first.id == block.id) {
-            groupedBlock.add(block);
-            found = true;
-            break;
-          }
-        }
-        if (!found) {
-          groupedBlocks.add([block]);
-        }
-      }
-    }
-    for (var block in defaultGroup) {
-      groupedBlocks.add([block]);
-    }
-    return groupedBlocks;
-  }
-
-  List<List<TimeBlock>> _mergeBlocksInColumns(List<TimeBlock> blocks) {
-    var mergedBlocks = <List<TimeBlock>>[];
-    // try to put blocks in the same column if the time doesn´t collide
-    for (var block in blocks) {
-      var mergeIndex = 0;
-
-      for (var mergedBlock in mergedBlocks) {
-        if (!mergedBlock.any((b) => b.collidesWith(block))) {
-          mergedBlock.add(block);
-          break;
-        } else {
-          mergeIndex++;
-        }
-      }
-      if (mergedBlocks.length == mergeIndex) {
-        mergedBlocks.add([block]);
-      }
-    }
-    return mergedBlocks;
+  Widget _showBlock(TimeBlock block) {
+    return Block(
+      start: block.start,
+      end: block.end,
+      startHour: widget.startHour,
+      hourHeight: widget.hourHeight,
+      blockWidth: widget.blockWidth,
+      blockColor: widget.blockColor,
+      child: block.child,
+    );
   }
 
   void _scrollToFirstBlock() {
diff --git a/lib/src/block.dart b/lib/src/widgets/block.dart
similarity index 100%
rename from lib/src/block.dart
rename to lib/src/widgets/block.dart
diff --git a/lib/src/table.dart b/lib/src/widgets/table.dart
similarity index 100%
rename from lib/src/table.dart
rename to lib/src/widgets/table.dart
diff --git a/lib/timetable.dart b/lib/timetable.dart
index 60a17d3..d7494b1 100644
--- a/lib/timetable.dart
+++ b/lib/timetable.dart
@@ -4,7 +4,8 @@ import 'package:flutter/material.dart';
 import 'package:flutter/scheduler.dart';
 
 part 'src/timetable.dart';
-part 'src/table.dart';
+part 'src/block_service.dart';
+part 'src/widgets/table.dart';
 part 'src/models/time_block.dart';
 part 'src/models/table_theme.dart';
-part 'src/block.dart';
+part 'src/widgets/block.dart';
diff --git a/test/block_service_test.dart b/test/block_service_test.dart
new file mode 100644
index 0000000..ac4e61e
--- /dev/null
+++ b/test/block_service_test.dart
@@ -0,0 +1,151 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:timetable/timetable.dart';
+
+void main() {
+  group('test collapseBlocks', () {
+    test('new block creation success', () {
+      //Arrange
+      var blocks = [
+        TimeBlock(
+          start: const TimeOfDay(hour: 2, minute: 0),
+          end: const TimeOfDay(hour: 2, minute: 15),
+          id: 5,
+        ),
+        TimeBlock(
+          start: const TimeOfDay(hour: 2, minute: 0),
+          end: const TimeOfDay(hour: 2, minute: 15),
+          id: 5,
+        ),
+        TimeBlock(
+          start: const TimeOfDay(hour: 2, minute: 15),
+          end: const TimeOfDay(hour: 2, minute: 30),
+          id: 6,
+        ),
+      ];
+
+      //Act
+      var result = collapseBlocks(blocks);
+
+      //Assert
+      expect(result.length, 2);
+      expect(
+        result.firstWhere((element) => element.id == 5).end,
+        const TimeOfDay(hour: 2, minute: 30),
+      );
+    });
+
+    test('elements without id ignored', () {
+      //Arrange
+      var blocks = [
+        TimeBlock(
+          start: const TimeOfDay(hour: 2, minute: 0),
+          end: const TimeOfDay(hour: 2, minute: 15),
+          id: 0, // default id is 0
+        ),
+        TimeBlock(
+          start: const TimeOfDay(hour: 2, minute: 0),
+          end: const TimeOfDay(hour: 2, minute: 15),
+          id: 0,
+        ),
+      ];
+
+      //Act
+      var result = collapseBlocks(blocks);
+
+      //Assert
+      expect(result.length, 2);
+      expect(result.first.end, const TimeOfDay(hour: 2, minute: 15));
+    });
+  });
+
+  group('test groupBlocksById', () {
+    test('groupBlocksById success', () {
+      //Arrange
+      var blocks = [
+        TimeBlock(
+          start: const TimeOfDay(hour: 2, minute: 0),
+          end: const TimeOfDay(hour: 2, minute: 15),
+          id: 5,
+        ),
+        TimeBlock(
+          start: const TimeOfDay(hour: 2, minute: 0),
+          end: const TimeOfDay(hour: 2, minute: 25),
+          id: 5,
+        ),
+        TimeBlock(
+          start: const TimeOfDay(hour: 2, minute: 20),
+          end: const TimeOfDay(hour: 2, minute: 30),
+          id: 6,
+        ),
+      ];
+
+      //Act
+      var result = groupBlocksById(blocks);
+
+      //Assert
+      expect(result.length, 2);
+    });
+
+    test('groupBlocksById id 0 ignored', () {
+      // Arrange
+      var blocks = [
+        TimeBlock(
+          start: const TimeOfDay(hour: 2, minute: 0),
+          end: const TimeOfDay(hour: 2, minute: 15),
+          id: 0,
+        ),
+        TimeBlock(
+          start: const TimeOfDay(hour: 2, minute: 0),
+          end: const TimeOfDay(hour: 2, minute: 25),
+          id: 0,
+        ),
+        TimeBlock(
+          start: const TimeOfDay(hour: 2, minute: 20),
+          end: const TimeOfDay(hour: 2, minute: 30),
+          id: 0,
+        ),
+      ];
+
+      //Act
+      var result = groupBlocksById(blocks);
+
+      //Assert
+      expect(result.length, 3);
+    });
+  });
+
+  group('test mergeBlocksInColumns', () {
+    test('mergeBlocksInColumns success', () {
+      //Arrange
+      var blocks = [
+        TimeBlock(
+          start: const TimeOfDay(hour: 2, minute: 0),
+          end: const TimeOfDay(hour: 6, minute: 15),
+          id: 1,
+        ),
+        TimeBlock(
+          start: const TimeOfDay(hour: 8, minute: 0),
+          end: const TimeOfDay(hour: 10, minute: 25),
+          id: 2,
+        ),
+        TimeBlock(
+          start: const TimeOfDay(hour: 12, minute: 20),
+          end: const TimeOfDay(hour: 14, minute: 30),
+          id: 3,
+        ),
+        TimeBlock(
+          start: const TimeOfDay(hour: 13, minute: 20),
+          end: const TimeOfDay(hour: 14, minute: 15),
+          id: 4,
+        ),
+      ];
+
+      //Act
+      var result = mergeBlocksInColumns(blocks);
+
+      //Assert
+      expect(result.length, 2);
+    });
+  });
+}