diff --git a/.gitignore b/.gitignore
index f8600d9..2760edd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 /tests/resources/generated
+/tests/coverage
 /vendor
 composer.lock
 /.idea
diff --git a/phpunit.xml b/phpunit.xml
index 975acc6..5de1e0f 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -14,4 +14,14 @@
         </testsuite>
     </testsuites>
 
+    <logging>
+        <log type="coverage-html" target="tests/coverage/"/>
+    </logging>
+
+    <filter>
+        <whitelist>
+            <directory suffix=".php">src/</directory>
+        </whitelist>
+    </filter>
+
 </phpunit>
diff --git a/src/Spout/Common/Escaper/CSV.php b/src/Spout/Common/Escaper/CSV.php
index efaebd6..4bc2d1a 100644
--- a/src/Spout/Common/Escaper/CSV.php
+++ b/src/Spout/Common/Escaper/CSV.php
@@ -13,6 +13,8 @@ class CSV implements EscaperInterface
     /**
      * Escapes the given string to make it compatible with CSV
      *
+     * @codeCoverageIgnore
+     *
      * @param string $string The string to escape
      * @return string The escaped string
      */
@@ -24,6 +26,8 @@ class CSV implements EscaperInterface
     /**
      * Unescapes the given string to make it compatible with CSV
      *
+     * @codeCoverageIgnore
+     *
      * @param string $string The string to unescape
      * @return string The unescaped string
      */
diff --git a/src/Spout/Common/Helper/GlobalFunctionsHelper.php b/src/Spout/Common/Helper/GlobalFunctionsHelper.php
index 8ce7ab5..5f22ed6 100644
--- a/src/Spout/Common/Helper/GlobalFunctionsHelper.php
+++ b/src/Spout/Common/Helper/GlobalFunctionsHelper.php
@@ -6,6 +6,8 @@ namespace Box\Spout\Common\Helper;
  * Class GlobalFunctionsHelper
  * This class wraps global functions to facilitate testing
  *
+ * @codeCoverageIgnore
+ *
  * @package Box\Spout\Common\Helper
  */
 class GlobalFunctionsHelper
diff --git a/src/Spout/Reader/Helper/XLSX/CellHelper.php b/src/Spout/Reader/Helper/XLSX/CellHelper.php
index 5802bff..7125ded 100644
--- a/src/Spout/Reader/Helper/XLSX/CellHelper.php
+++ b/src/Spout/Reader/Helper/XLSX/CellHelper.php
@@ -25,7 +25,7 @@ class CellHelper
     {
         $existingIndexes = array_keys($dataArray);
 
-        $newIndexes = array_fill_keys(range(min($existingIndexes), max($existingIndexes)), $fillValue);
+        $newIndexes = array_fill_keys(range(0, max($existingIndexes)), $fillValue);
         $dataArray += $newIndexes;
 
         ksort($dataArray);
diff --git a/src/Spout/Writer/AbstractWriter.php b/src/Spout/Writer/AbstractWriter.php
index 64f7440..68d452f 100644
--- a/src/Spout/Writer/AbstractWriter.php
+++ b/src/Spout/Writer/AbstractWriter.php
@@ -89,6 +89,8 @@ abstract class AbstractWriter implements WriterInterface
      * Inits the writer and opens it to accept data.
      * By using this method, the data will be outputted directly to the browser.
      *
+     * @codeCoverageIgnore
+     *
      * @param  string $outputFileName Name of the output file that will contain the data. If a path is passed in, only the file name will be kept
      * @return \Box\Spout\Writer\AbstractWriter
      * @throws \Box\Spout\Common\Exception\IOException If the writer cannot be opened
diff --git a/tests/Spout/Reader/Helper/XLSX/CellHelperTest.php b/tests/Spout/Reader/Helper/XLSX/CellHelperTest.php
new file mode 100644
index 0000000..8851b33
--- /dev/null
+++ b/tests/Spout/Reader/Helper/XLSX/CellHelperTest.php
@@ -0,0 +1,60 @@
+<?php
+
+namespace Box\Spout\Reader\Helper\XLSX;
+
+/**
+ * Class CellHelperTest
+ *
+ * @package Box\Spout\Reader\Helper\XLSX
+ */
+class CellHelperTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @return void
+     */
+    public function testFillMissingArrayIndexes()
+    {
+        $arrayToFill = [1 => 1, 3 => 3];
+        $filledArray = CellHelper::fillMissingArrayIndexes($arrayToFill, 'FILL');
+
+        $expectedFilledArray = ['FILL', 1, 'FILL', 3];
+        $this->assertEquals($expectedFilledArray, $filledArray);
+    }
+
+    /**
+     * @return array
+     */
+    public function dataProviderForTestGetColumnIndexFromCellIndex()
+    {
+        return [
+            ['A1', 0],
+            ['Z3', 25],
+            ['AA5', 26],
+            ['AB24', 27],
+            ['BC5', 54],
+            ['BCZ99', 1455],
+        ];
+    }
+
+    /**
+     * @dataProvider dataProviderForTestGetColumnIndexFromCellIndex
+     *
+     * @param string $cellIndex
+     * @param int $expectedColumnIndex
+     * @return void
+     */
+    public function testGetColumnIndexFromCellIndex($cellIndex, $expectedColumnIndex)
+    {
+        $this->assertEquals($expectedColumnIndex, CellHelper::getColumnIndexFromCellIndex($cellIndex));
+    }
+
+    /**
+     * @expectedException \Box\Spout\Common\Exception\InvalidArgumentException
+     *
+     * @return void
+     */
+    public function testGetColumnIndexFromCellIndexShouldThrowIfInvalidCellIndex()
+    {
+        CellHelper::getColumnIndexFromCellIndex('InvalidCellIndex');
+    }
+}
diff --git a/tests/Spout/Reader/ReaderFactoryTest.php b/tests/Spout/Reader/ReaderFactoryTest.php
new file mode 100644
index 0000000..57a0b55
--- /dev/null
+++ b/tests/Spout/Reader/ReaderFactoryTest.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace Box\Spout\Reader;
+
+/**
+ * Class ReaderFactoryTest
+ *
+ * @package Box\Spout\Writer
+ */
+class ReaderFactoryTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @expectedException \Box\Spout\Common\Exception\UnsupportedTypeException
+     *
+     * @return void
+     */
+    public function testCreateReaderShouldThrowWithUnsupportedType()
+    {
+        ReaderFactory::create('unsupportedType');
+    }
+}
diff --git a/tests/Spout/Reader/XLSXTest.php b/tests/Spout/Reader/XLSXTest.php
index 20e89d3..23d26bc 100644
--- a/tests/Spout/Reader/XLSXTest.php
+++ b/tests/Spout/Reader/XLSXTest.php
@@ -153,6 +153,19 @@ class XLSXTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals($expectedRows, $allRows);
     }
 
+    /**
+     * @return void
+     */
+    public function testReadShouldPreserveSpaceIfSpecified()
+    {
+        $allRows = $this->getAllRowsForFile('sheet_with_preserve_space_shared_strings.xlsx');
+
+        $expectedRows = [
+            ['  s1--A1', 's1--B1  ', '  s1--C1  '],
+        ];
+        $this->assertEquals($expectedRows, $allRows);
+    }
+
     /**
      * @return void
      */
@@ -171,7 +184,7 @@ class XLSXTest extends \PHPUnit_Framework_TestCase
     {
         $allRows = $this->getAllRowsForFile('billion_laughs_test_file.xlsx');
 
-        $expectedMaxMemoryUsage = 10 * 1024 * 1024; // 10MB
+        $expectedMaxMemoryUsage = 20 * 1024 * 1024; // 20MB
         $this->assertLessThan($expectedMaxMemoryUsage, memory_get_peak_usage(true), 'Entities should not be expanded and therefore consume all the memory.');
 
         $expectedFirstRow = ['s1--A1', 's1--B1', 's1--C1', 's1--D1', 's1--E1'];
diff --git a/tests/Spout/Writer/CSVTest.php b/tests/Spout/Writer/CSVTest.php
index 2d1b207..ef71b87 100644
--- a/tests/Spout/Writer/CSVTest.php
+++ b/tests/Spout/Writer/CSVTest.php
@@ -49,6 +49,16 @@ class CSVTest extends \PHPUnit_Framework_TestCase
         $writer->close();
     }
 
+    /**
+     * @expectedException \Box\Spout\Common\Exception\InvalidArgumentException
+     */
+    public function testAddRowsShouldThrowExceptionIfRowsAreNotArrayOfArrays()
+    {
+        $writer = WriterFactory::create(Type::CSV);
+        $writer->addRows(['csv--11', 'csv--12']);
+        $writer->close();
+    }
+
     /**
      * @return void
      */
diff --git a/tests/Spout/Writer/WriterFactoryTest.php b/tests/Spout/Writer/WriterFactoryTest.php
new file mode 100644
index 0000000..528eff3
--- /dev/null
+++ b/tests/Spout/Writer/WriterFactoryTest.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace Box\Spout\Writer;
+
+/**
+ * Class WriterFactoryTest
+ *
+ * @package Box\Spout\Writer
+ */
+class WriterFactoryTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @expectedException \Box\Spout\Common\Exception\UnsupportedTypeException
+     *
+     * @return void
+     */
+    public function testCreateWriterShouldThrowWithUnsupportedType()
+    {
+        WriterFactory::create('unsupportedType');
+    }
+}
diff --git a/tests/resources/xlsx/sheet_with_preserve_space_shared_strings.xlsx b/tests/resources/xlsx/sheet_with_preserve_space_shared_strings.xlsx
new file mode 100644
index 0000000..3936a94
Binary files /dev/null and b/tests/resources/xlsx/sheet_with_preserve_space_shared_strings.xlsx differ