diff --git a/include/xlnt/cell/cell.hpp b/include/xlnt/cell/cell.hpp
index f00955b5..ebe37f8d 100644
--- a/include/xlnt/cell/cell.hpp
+++ b/include/xlnt/cell/cell.hpp
@@ -77,7 +77,8 @@ public:
     cell();
     cell(worksheet ws, const cell_reference &reference, const std::string &initial_value = std::string());
     
-    std::string get_value() const;
+    std::string get_internal_value_string() const;
+    long double get_internal_value_numeric() const;
     
     std::string get_column() const;
     row_t get_row() const;
diff --git a/include/xlnt/common/datetime.hpp b/include/xlnt/common/datetime.hpp
index 92d06134..5d768b5a 100644
--- a/include/xlnt/common/datetime.hpp
+++ b/include/xlnt/common/datetime.hpp
@@ -28,6 +28,8 @@ namespace xlnt {
 
 struct date
 {
+    static date today();
+
     date(int year, int month, int day)
         : year(year), month(month), day(day)
     {
@@ -40,6 +42,8 @@ struct date
 
 struct time
 {
+    static time now();
+
     time(int hour = 0, int minute = 0, int second = 0, int microsecond = 0)
         : hour(hour), minute(minute), second(second), microsecond(microsecond)
     {
diff --git a/source/cell.cpp b/source/cell.cpp
index f51f6312..0f9e1e00 100644
--- a/source/cell.cpp
+++ b/source/cell.cpp
@@ -45,22 +45,29 @@ cell::cell(worksheet worksheet, const cell_reference &reference, const std::stri
     }
 }
 
-std::string cell::get_value() const
+std::string cell::get_internal_value_string() const
 {
     switch(d_->type_)
     {
     case type::string:
         return d_->string_value;
-    case type::numeric:
-            return std::floor(d_->numeric_value) == d_->numeric_value ? std::to_string((long long)d_->numeric_value) : std::to_string(d_->numeric_value);
     case type::formula:
         return d_->string_value;
     case type::error:
         return d_->string_value;
-    case type::null:
-        return "";
+    default:
+        throw std::runtime_error("bad enum");
+    }
+}
+
+long double cell::get_internal_value_numeric() const
+{
+    switch(d_->type_)
+    {
+    case type::numeric:
+        return d_->numeric_value;
     case type::boolean:
-        return d_->numeric_value != 0 ? "1" : "0";
+        return d_->numeric_value == 0 ? 0 : 1;
     default:
         throw std::runtime_error("bad enum");
     }
@@ -150,6 +157,14 @@ cell::type cell::data_type_for_value(const std::string &value)
             {
                 return type::boolean;
             }
+            if(value.back() == '%')
+            {
+                strtod(value.substr(0, value.length() - 1).c_str(), &p);
+                if(*p == 0)
+                {
+                    return type::numeric;
+                }
+            }
             return type::string;
         }
         else
@@ -398,8 +413,12 @@ cell &cell::operator=(const std::string &value)
 	      d_->is_date_ = true;
 	      d_->numeric_value = time(value).to_number();
 	    }
-	  else
+	  else if(value.back() == '%')
 	    {
+            d_->numeric_value = std::stod(value.substr(0, value.length() - 1)) / 100;
+        }
+        else
+        {
 	      d_->numeric_value = std::stod(value);
 	    }
             break;
diff --git a/source/datetime.cpp b/source/datetime.cpp
index 2c595321..c297aa3a 100644
--- a/source/datetime.cpp
+++ b/source/datetime.cpp
@@ -48,6 +48,13 @@ double time::to_number() const
     return number;
 }
 
+date date::today()
+{
+    std::time_t raw_time = std::time(0);
+    std::tm now = *std::localtime(&raw_time);
+    return date(now.tm_year, now.tm_mon + 1, now.tm_mday);
+}
+
 datetime datetime::now()
 {
     std::time_t raw_time = std::time(0);
diff --git a/source/detail/cell_impl.hpp b/source/detail/cell_impl.hpp
index c2b9d786..49a01126 100644
--- a/source/detail/cell_impl.hpp
+++ b/source/detail/cell_impl.hpp
@@ -25,8 +25,8 @@ struct cell_impl
     relationship hyperlink_;
     column_t column;
     row_t row;
-    bool merged;
     style *style_;
+    bool merged;
     bool is_date_;
 };
     
diff --git a/source/workbook.cpp b/source/workbook.cpp
index 87e93743..ea8866aa 100644
--- a/source/workbook.cpp
+++ b/source/workbook.cpp
@@ -4,7 +4,9 @@
 #include <sstream>
 #include <pugixml.hpp>
 
+#ifdef _WIN32
 #include <Windows.h>
+#endif
 
 #include "workbook/workbook.hpp"
 #include "common/exceptions.hpp"
diff --git a/source/writer.cpp b/source/writer.cpp
index f4823f52..9fe42a37 100644
--- a/source/writer.cpp
+++ b/source/writer.cpp
@@ -273,7 +273,7 @@ std::string writer::write_worksheet(worksheet ws, const std::vector<std::string>
                     int match_index = -1;
                     for(int i = 0; i < (int)string_table.size(); i++)
                     {
-                        if(string_table[i] == cell.get_value())
+                        if(string_table[i] == cell.get_internal_value_string())
                         {
                             match_index = i;
                             break;
@@ -284,7 +284,7 @@ std::string writer::write_worksheet(worksheet ws, const std::vector<std::string>
                     {
                         cell_node.append_attribute("t").set_value("inlineStr");
                         auto inline_string_node = cell_node.append_child("is");
-                        inline_string_node.append_child("t").text().set(cell.get_value().c_str());
+                        inline_string_node.append_child("t").text().set(cell.get_internal_value_string().c_str());
                     }
                     else
                     {
@@ -301,17 +301,17 @@ std::string writer::write_worksheet(worksheet ws, const std::vector<std::string>
                         {
                             cell_node.append_attribute("t").set_value("b");
                             auto value_node = cell_node.append_child("v");
-                            value_node.text().set(cell.get_value().c_str());
+                            value_node.text().set(cell.get_internal_value_numeric() == 0 ? 0 : 1);
                         }
                         else if(cell.get_data_type() == cell::type::numeric)
                         {
                             cell_node.append_attribute("t").set_value("n");
                             auto value_node = cell_node.append_child("v");
-                            value_node.text().set(cell.get_value().c_str());
+                            value_node.text().set((double)cell.get_internal_value_numeric());
                         }
                         else if(cell.get_data_type() == cell::type::formula)
                         {
-                            cell_node.append_child("f").text().set(cell.get_value().substr(1).c_str());
+                            cell_node.append_child("f").text().set(cell.get_internal_value_string().substr(1).c_str());
                             cell_node.append_child("v");
                         }
                     }
@@ -664,7 +664,8 @@ std::string writer::write_theme()
      doc.print(ss);
      return ss.str();
      */
-    std::array<unsigned char, 10421> theme1_xml = {
+    std::array<unsigned char, 10421> theme1_xml = 
+    {{
         0x3c, 0x3f, 0x78, 0x6d, 0x6c, 0x20, 0x76, 0x65, 0x72, 0x73, 0x69, 0x6f,
         0x6e, 0x3d, 0x22, 0x31, 0x2e, 0x30, 0x22, 0x3f, 0x3e, 0x0d, 0x0a, 0x3c,
         0x61, 0x3a, 0x74, 0x68, 0x65, 0x6d, 0x65, 0x20, 0x78, 0x6d, 0x6c, 0x6e,
@@ -1534,7 +1535,7 @@ std::string writer::write_theme()
         0x61, 0x43, 0x6c, 0x72, 0x53, 0x63, 0x68, 0x65, 0x6d, 0x65, 0x4c, 0x73,
         0x74, 0x2f, 0x3e, 0x0d, 0x0a, 0x3c, 0x2f, 0x61, 0x3a, 0x74, 0x68, 0x65,
         0x6d, 0x65, 0x3e, 0x0d, 0x0a
-    };
+    }};
 
     return std::string(theme1_xml.begin(), theme1_xml.end());
 }
diff --git a/tests/runner-autogen.cpp b/tests/runner-autogen.cpp
index 679bde3e..c6a6df00 100644
--- a/tests/runner-autogen.cpp
+++ b/tests/runner-autogen.cpp
@@ -21,7 +21,7 @@ int main( int argc, char *argv[] ) {
     return status;
 }
 bool suite_test_cell_init = false;
-#include "C:\Users\taf656\Development\xlnt\tests\test_cell.hpp"
+#include "/Users/thomas/Development/xlnt/tests/test_cell.hpp"
 
 static test_cell suite_test_cell;
 
@@ -42,149 +42,203 @@ public:
 
 static class TestDescription_suite_test_cell_test_zero_row : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_zero_row() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 24, "test_zero_row" ) {}
+ TestDescription_suite_test_cell_test_zero_row() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 25, "test_zero_row" ) {}
  void runTest() { suite_test_cell.test_zero_row(); }
 } testDescription_suite_test_cell_test_zero_row;
 
 static class TestDescription_suite_test_cell_test_absolute : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_absolute() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 29, "test_absolute" ) {}
+ TestDescription_suite_test_cell_test_absolute() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 31, "test_absolute" ) {}
  void runTest() { suite_test_cell.test_absolute(); }
 } testDescription_suite_test_cell_test_absolute;
 
 static class TestDescription_suite_test_cell_test_absolute_multiple : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_absolute_multiple() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 34, "test_absolute_multiple" ) {}
+ TestDescription_suite_test_cell_test_absolute_multiple() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 36, "test_absolute_multiple" ) {}
  void runTest() { suite_test_cell.test_absolute_multiple(); }
 } testDescription_suite_test_cell_test_absolute_multiple;
 
 static class TestDescription_suite_test_cell_test_column_index : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_column_index() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 39, "test_column_index" ) {}
+ TestDescription_suite_test_cell_test_column_index() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 41, "test_column_index" ) {}
  void runTest() { suite_test_cell.test_column_index(); }
 } testDescription_suite_test_cell_test_column_index;
 
 static class TestDescription_suite_test_cell_test_bad_column_index : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_bad_column_index() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 69, "test_bad_column_index" ) {}
+ TestDescription_suite_test_cell_test_bad_column_index() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 71, "test_bad_column_index" ) {}
  void runTest() { suite_test_cell.test_bad_column_index(); }
 } testDescription_suite_test_cell_test_bad_column_index;
 
 static class TestDescription_suite_test_cell_test_column_letter_boundries : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_column_letter_boundries() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 77, "test_column_letter_boundries" ) {}
+ TestDescription_suite_test_cell_test_column_letter_boundries() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 79, "test_column_letter_boundries" ) {}
  void runTest() { suite_test_cell.test_column_letter_boundries(); }
 } testDescription_suite_test_cell_test_column_letter_boundries;
 
 static class TestDescription_suite_test_cell_test_column_letter : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_column_letter() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 86, "test_column_letter" ) {}
+ TestDescription_suite_test_cell_test_column_letter() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 88, "test_column_letter" ) {}
  void runTest() { suite_test_cell.test_column_letter(); }
 } testDescription_suite_test_cell_test_column_letter;
 
 static class TestDescription_suite_test_cell_test_initial_value : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_initial_value() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 96, "test_initial_value" ) {}
+ TestDescription_suite_test_cell_test_initial_value() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 98, "test_initial_value" ) {}
  void runTest() { suite_test_cell.test_initial_value(); }
 } testDescription_suite_test_cell_test_initial_value;
 
+static class TestDescription_suite_test_cell_test_1st : public CxxTest::RealTestDescription {
+public:
+ TestDescription_suite_test_cell_test_1st() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 106, "test_1st" ) {}
+ void runTest() { suite_test_cell.test_1st(); }
+} testDescription_suite_test_cell_test_1st;
+
 static class TestDescription_suite_test_cell_test_null : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_null() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 104, "test_null" ) {}
+ TestDescription_suite_test_cell_test_null() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 114, "test_null" ) {}
  void runTest() { suite_test_cell.test_null(); }
 } testDescription_suite_test_cell_test_null;
 
 static class TestDescription_suite_test_cell_test_numeric : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_numeric() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 112, "test_numeric" ) {}
+ TestDescription_suite_test_cell_test_numeric() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 123, "test_numeric" ) {}
  void runTest() { suite_test_cell.test_numeric(); }
 } testDescription_suite_test_cell_test_numeric;
 
 static class TestDescription_suite_test_cell_test_string : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_string() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 154, "test_string" ) {}
+ TestDescription_suite_test_cell_test_string() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 165, "test_string" ) {}
  void runTest() { suite_test_cell.test_string(); }
 } testDescription_suite_test_cell_test_string;
 
 static class TestDescription_suite_test_cell_test_single_dot : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_single_dot() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 163, "test_single_dot" ) {}
+ TestDescription_suite_test_cell_test_single_dot() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 174, "test_single_dot" ) {}
  void runTest() { suite_test_cell.test_single_dot(); }
 } testDescription_suite_test_cell_test_single_dot;
 
 static class TestDescription_suite_test_cell_test_formula : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_formula() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 171, "test_formula" ) {}
+ TestDescription_suite_test_cell_test_formula() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 182, "test_formula" ) {}
  void runTest() { suite_test_cell.test_formula(); }
 } testDescription_suite_test_cell_test_formula;
 
 static class TestDescription_suite_test_cell_test_boolean : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_boolean() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 179, "test_boolean" ) {}
+ TestDescription_suite_test_cell_test_boolean() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 192, "test_boolean" ) {}
  void runTest() { suite_test_cell.test_boolean(); }
 } testDescription_suite_test_cell_test_boolean;
 
 static class TestDescription_suite_test_cell_test_leading_zero : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_leading_zero() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 189, "test_leading_zero" ) {}
+ TestDescription_suite_test_cell_test_leading_zero() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 202, "test_leading_zero" ) {}
  void runTest() { suite_test_cell.test_leading_zero(); }
 } testDescription_suite_test_cell_test_leading_zero;
 
 static class TestDescription_suite_test_cell_test_error_codes : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_error_codes() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 197, "test_error_codes" ) {}
+ TestDescription_suite_test_cell_test_error_codes() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 210, "test_error_codes" ) {}
  void runTest() { suite_test_cell.test_error_codes(); }
 } testDescription_suite_test_cell_test_error_codes;
 
+static class TestDescription_suite_test_cell_test_insert_float : public CxxTest::RealTestDescription {
+public:
+ TestDescription_suite_test_cell_test_insert_float() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 222, "test_insert_float" ) {}
+ void runTest() { suite_test_cell.test_insert_float(); }
+} testDescription_suite_test_cell_test_insert_float;
+
+static class TestDescription_suite_test_cell_test_insert_percentage : public CxxTest::RealTestDescription {
+public:
+ TestDescription_suite_test_cell_test_insert_percentage() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 230, "test_insert_percentage" ) {}
+ void runTest() { suite_test_cell.test_insert_percentage(); }
+} testDescription_suite_test_cell_test_insert_percentage;
+
+static class TestDescription_suite_test_cell_test_insert_datetime : public CxxTest::RealTestDescription {
+public:
+ TestDescription_suite_test_cell_test_insert_datetime() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 238, "test_insert_datetime" ) {}
+ void runTest() { suite_test_cell.test_insert_datetime(); }
+} testDescription_suite_test_cell_test_insert_datetime;
+
+static class TestDescription_suite_test_cell_test_insert_date : public CxxTest::RealTestDescription {
+public:
+ TestDescription_suite_test_cell_test_insert_date() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 246, "test_insert_date" ) {}
+ void runTest() { suite_test_cell.test_insert_date(); }
+} testDescription_suite_test_cell_test_insert_date;
+
+static class TestDescription_suite_test_cell_test_internal_date : public CxxTest::RealTestDescription {
+public:
+ TestDescription_suite_test_cell_test_internal_date() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 254, "test_internal_date" ) {}
+ void runTest() { suite_test_cell.test_internal_date(); }
+} testDescription_suite_test_cell_test_internal_date;
+
+static class TestDescription_suite_test_cell_test_datetime_interpretation : public CxxTest::RealTestDescription {
+public:
+ TestDescription_suite_test_cell_test_datetime_interpretation() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 263, "test_datetime_interpretation" ) {}
+ void runTest() { suite_test_cell.test_datetime_interpretation(); }
+} testDescription_suite_test_cell_test_datetime_interpretation;
+
+static class TestDescription_suite_test_cell_test_date_interpretation : public CxxTest::RealTestDescription {
+public:
+ TestDescription_suite_test_cell_test_date_interpretation() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 273, "test_date_interpretation" ) {}
+ void runTest() { suite_test_cell.test_date_interpretation(); }
+} testDescription_suite_test_cell_test_date_interpretation;
+
+static class TestDescription_suite_test_cell_test_number_format_style : public CxxTest::RealTestDescription {
+public:
+ TestDescription_suite_test_cell_test_number_format_style() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 283, "test_number_format_style" ) {}
+ void runTest() { suite_test_cell.test_number_format_style(); }
+} testDescription_suite_test_cell_test_number_format_style;
+
 static class TestDescription_suite_test_cell_test_data_type_check : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_data_type_check() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 210, "test_data_type_check" ) {}
+ TestDescription_suite_test_cell_test_data_type_check() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 291, "test_data_type_check" ) {}
  void runTest() { suite_test_cell.test_data_type_check(); }
 } testDescription_suite_test_cell_test_data_type_check;
 
 static class TestDescription_suite_test_cell_test_set_bad_type : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_set_bad_type() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 227, "test_set_bad_type" ) {}
+ TestDescription_suite_test_cell_test_set_bad_type() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 308, "test_set_bad_type" ) {}
  void runTest() { suite_test_cell.test_set_bad_type(); }
 } testDescription_suite_test_cell_test_set_bad_type;
 
 static class TestDescription_suite_test_cell_test_time : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_time() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 245, "test_time" ) {}
+ TestDescription_suite_test_cell_test_time() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 326, "test_time" ) {}
  void runTest() { suite_test_cell.test_time(); }
 } testDescription_suite_test_cell_test_time;
 
 static class TestDescription_suite_test_cell_test_date_format_on_non_date : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_date_format_on_non_date() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 259, "test_date_format_on_non_date" ) {}
+ TestDescription_suite_test_cell_test_date_format_on_non_date() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 340, "test_date_format_on_non_date" ) {}
  void runTest() { suite_test_cell.test_date_format_on_non_date(); }
 } testDescription_suite_test_cell_test_date_format_on_non_date;
 
 static class TestDescription_suite_test_cell_test_set_get_date : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_set_get_date() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 269, "test_set_get_date" ) {}
+ TestDescription_suite_test_cell_test_set_get_date() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 350, "test_set_get_date" ) {}
  void runTest() { suite_test_cell.test_set_get_date(); }
 } testDescription_suite_test_cell_test_set_get_date;
 
 static class TestDescription_suite_test_cell_test_repr : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_repr() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 280, "test_repr" ) {}
+ TestDescription_suite_test_cell_test_repr() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 361, "test_repr" ) {}
  void runTest() { suite_test_cell.test_repr(); }
 } testDescription_suite_test_cell_test_repr;
 
 static class TestDescription_suite_test_cell_test_is_date : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_is_date() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 288, "test_is_date" ) {}
+ TestDescription_suite_test_cell_test_is_date() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 369, "test_is_date" ) {}
  void runTest() { suite_test_cell.test_is_date(); }
 } testDescription_suite_test_cell_test_is_date;
 
 static class TestDescription_suite_test_cell_test_is_not_date_color_format : public CxxTest::RealTestDescription {
 public:
- TestDescription_suite_test_cell_test_is_not_date_color_format() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 302, "test_is_not_date_color_format" ) {}
+ TestDescription_suite_test_cell_test_is_not_date_color_format() : CxxTest::RealTestDescription( Tests_test_cell, suiteDescription_test_cell, 383, "test_is_not_date_color_format" ) {}
  void runTest() { suite_test_cell.test_is_not_date_color_format(); }
 } testDescription_suite_test_cell_test_is_not_date_color_format;
 
-#include "C:\Users\taf656\Development\xlnt\tests\test_chart.hpp"
+#include "/Users/thomas/Development/xlnt/tests/test_chart.hpp"
 
 static test_chart suite_test_chart;
 
@@ -275,7 +329,7 @@ public:
  void runTest() { suite_test_chart.test_write_chart_scatter(); }
 } testDescription_suite_test_chart_test_write_chart_scatter;
 
-#include "C:\Users\taf656\Development\xlnt\tests\test_dump.hpp"
+#include "/Users/thomas/Development/xlnt/tests/test_dump.hpp"
 
 static test_dump suite_test_dump;
 
@@ -312,7 +366,7 @@ public:
  void runTest() { suite_test_dump.test_append_after_save(); }
 } testDescription_suite_test_dump_test_append_after_save;
 
-#include "C:\Users\taf656\Development\xlnt\tests\test_named_range.hpp"
+#include "/Users/thomas/Development/xlnt/tests/test_named_range.hpp"
 
 static test_named_range suite_test_named_range;
 
@@ -403,7 +457,7 @@ public:
  void runTest() { suite_test_named_range.test_can_be_saved(); }
 } testDescription_suite_test_named_range_test_can_be_saved;
 
-#include "C:\Users\taf656\Development\xlnt\tests\test_number_format.hpp"
+#include "/Users/thomas/Development/xlnt/tests/test_number_format.hpp"
 
 static test_number_format suite_test_number_format;
 
@@ -506,7 +560,7 @@ public:
  void runTest() { suite_test_number_format.test_mac_date(); }
 } testDescription_suite_test_number_format_test_mac_date;
 
-#include "C:\Users\taf656\Development\xlnt\tests\test_props.hpp"
+#include "/Users/thomas/Development/xlnt/tests/test_props.hpp"
 
 static test_props suite_test_props;
 
@@ -549,7 +603,7 @@ public:
  void runTest() { suite_test_props.test_write_properties_app(); }
 } testDescription_suite_test_props_test_write_properties_app;
 
-#include "C:\Users\taf656\Development\xlnt\tests\test_read.hpp"
+#include "/Users/thomas/Development/xlnt/tests/test_read.hpp"
 
 static test_read suite_test_read;
 
@@ -682,7 +736,7 @@ public:
  void runTest() { suite_test_read.test_read_date_value(); }
 } testDescription_suite_test_read_test_read_date_value;
 
-#include "C:\Users\taf656\Development\xlnt\tests\test_strings.hpp"
+#include "/Users/thomas/Development/xlnt/tests/test_strings.hpp"
 
 static test_strings suite_test_strings;
 
@@ -713,7 +767,7 @@ public:
  void runTest() { suite_test_strings.test_formatted_string_table(); }
 } testDescription_suite_test_strings_test_formatted_string_table;
 
-#include "C:\Users\taf656\Development\xlnt\tests\test_style.hpp"
+#include "/Users/thomas/Development/xlnt/tests/test_style.hpp"
 
 static test_style suite_test_style;
 
@@ -810,7 +864,7 @@ public:
  void runTest() { suite_test_style.test_read_cell_style(); }
 } testDescription_suite_test_style_test_read_cell_style;
 
-#include "C:\Users\taf656\Development\xlnt\tests\test_theme.hpp"
+#include "/Users/thomas/Development/xlnt/tests/test_theme.hpp"
 
 static test_theme suite_test_theme;
 
@@ -823,7 +877,7 @@ public:
  void runTest() { suite_test_theme.test_write_theme(); }
 } testDescription_suite_test_theme_test_write_theme;
 
-#include "C:\Users\taf656\Development\xlnt\tests\test_workbook.hpp"
+#include "/Users/thomas/Development/xlnt/tests/test_workbook.hpp"
 
 static test_workbook suite_test_workbook;
 
@@ -950,7 +1004,7 @@ public:
  void runTest() { suite_test_workbook.test_write_regular_float(); }
 } testDescription_suite_test_workbook_test_write_regular_float;
 
-#include "C:\Users\taf656\Development\xlnt\tests\test_worksheet.hpp"
+#include "/Users/thomas/Development/xlnt/tests/test_worksheet.hpp"
 
 static test_worksheet suite_test_worksheet;
 
@@ -1119,7 +1173,7 @@ public:
  void runTest() { suite_test_worksheet.test_printer_settings(); }
 } testDescription_suite_test_worksheet_test_printer_settings;
 
-#include "C:\Users\taf656\Development\xlnt\tests\test_write.hpp"
+#include "/Users/thomas/Development/xlnt/tests/test_write.hpp"
 
 static test_write suite_test_write;
 
diff --git a/tests/test_backend.hpp b/tests/test_backend.hpp
deleted file mode 100644
index 5723b84f..00000000
--- a/tests/test_backend.hpp
+++ /dev/null
@@ -1,11 +0,0 @@
-#pragma once
-
-#include <iostream>
-#include <cxxtest/TestSuite.h>
-
-#include <xlnt/xlnt.hpp>
-
-class test_backend : public CxxTest::TestSuite
-{
-public:
-};
diff --git a/tests/test_cell.hpp b/tests/test_cell.hpp
index 7fc3c169..5d8a1359 100644
--- a/tests/test_cell.hpp
+++ b/tests/test_cell.hpp
@@ -18,12 +18,14 @@ public:
 
     void test_invalid_coordinate()
     {
-        TS_ASSERT_THROWS(xlnt::cell_reference("AAA"), xlnt::cell_coordinates_exception);
+        TS_ASSERT_THROWS(xlnt::cell_reference("AAA"), 
+            xlnt::cell_coordinates_exception);
     }
 
     void test_zero_row()
     {
-      TS_ASSERT_THROWS(xlnt::cell_reference("AQ0"), xlnt::cell_coordinates_exception);
+        TS_ASSERT_THROWS(xlnt::cell_reference("AQ0"), 
+            xlnt::cell_coordinates_exception);
     }
 
     void test_absolute()
@@ -70,7 +72,7 @@ public:
     {
 	for(auto bad_string : {"JJJJ", "", "$", "1"})
         {
-	    TS_ASSERT_THROWS(xlnt::cell_reference::column_index_from_string(bad_string), xlnt::column_string_index_exception);
+            TS_ASSERT_THROWS(xlnt::cell_reference::column_index_from_string(bad_string), xlnt::column_string_index_exception);
         }
     }
 
@@ -101,7 +103,7 @@ public:
         TS_ASSERT_EQUALS(xlnt::cell::type::numeric, cell.get_data_type());
     }
 
-    void test_null()
+    void test_1st()
     {
         xlnt::worksheet ws = wb.create_sheet();
         xlnt::cell cell(ws, "A1");
@@ -109,6 +111,15 @@ public:
         TS_ASSERT_EQUALS(xlnt::cell::type::null, cell.get_data_type());
     }
 
+    void test_null()
+    {
+        xlnt::worksheet ws = wb.create_sheet();
+        xlnt::cell cell(ws, "A1", "17.5");
+        cell.set_null();
+
+        TS_ASSERT_EQUALS(xlnt::cell::type::null, cell.get_data_type());
+    }
+
     void test_numeric()
     {
         xlnt::worksheet ws = wb.create_sheet();
@@ -174,6 +185,8 @@ public:
         xlnt::cell cell(ws, "A1");
         cell = "=42";
         TS_ASSERT_EQUALS(xlnt::cell::type::formula, cell.get_data_type());
+        cell = "=if(A1<4;-1;1)";
+        TS_ASSERT_EQUALS(xlnt::cell::type::formula, cell.get_data_type());
     }
 
     void test_boolean()
@@ -206,6 +219,74 @@ public:
         }
     }
 
+    void test_insert_float()
+    {
+        xlnt::worksheet ws = wb.create_sheet();
+        xlnt::cell cell(ws, "A1");
+        cell = 3.14;
+        TS_ASSERT_EQUALS(xlnt::cell::type::numeric, cell.get_data_type());
+    }
+
+    void test_insert_percentage()
+    {
+        xlnt::worksheet ws = wb.create_sheet();
+        xlnt::cell cell(ws, "A1");
+        cell = "3.14%";
+        TS_ASSERT_EQUALS(0.0314, cell.get_internal_value_numeric());
+    }
+
+    void test_insert_datetime()
+    {
+        xlnt::worksheet ws = wb.create_sheet();
+        xlnt::cell cell(ws, "A1");
+        cell = xlnt::date::today();
+        TS_ASSERT_EQUALS(xlnt::cell::type::numeric, cell.get_data_type());
+    }
+
+    void test_insert_date()
+    {
+        xlnt::worksheet ws = wb.create_sheet();
+        xlnt::cell cell(ws, "A1");
+        cell = xlnt::datetime::now();
+        TS_ASSERT_EQUALS(xlnt::cell::type::numeric, cell.get_data_type());
+    }
+
+    void test_internal_date()
+    {
+        xlnt::worksheet ws = wb.create_sheet();
+        xlnt::cell cell(ws, "A1");
+        xlnt::datetime dt(2010, 7, 13, 6, 37, 41);
+        cell = dt;
+        TS_ASSERT_EQUALS(40372.27616898148, cell.get_internal_value_numeric());
+    }
+
+    void test_datetime_interpretation()
+    {
+        xlnt::worksheet ws = wb.create_sheet();
+        xlnt::cell cell(ws, "A1");
+        xlnt::datetime dt(2010, 7, 13, 6, 37, 41);
+        cell = dt;
+        TS_ASSERT_EQUALS(cell, dt);
+        TS_ASSERT_EQUALS(cell.get_internal_value_numeric(), 40372.27616898148);
+    }
+
+    void test_date_interpretation()
+    {
+        xlnt::worksheet ws = wb.create_sheet();
+        xlnt::cell cell(ws, "A1");
+        xlnt::date dt(2010, 7, 13);
+        cell = dt;
+        TS_ASSERT_EQUALS(cell, xlnt::datetime(2010, 7, 13, 0, 0));
+        TS_ASSERT_EQUALS(cell.get_internal_value_numeric(), 40372);
+    }
+
+    void test_number_format_style()
+    {
+        xlnt::worksheet ws = wb.create_sheet();
+        xlnt::cell cell(ws, "A1");
+        cell = "12.6%";
+        TS_ASSERT_EQUALS(xlnt::number_format::format::percentage, cell.get_style().get_number_format().get_format_code());
+    }
 
     void test_data_type_check()
     {
diff --git a/tests/test_workbook.hpp b/tests/test_workbook.hpp
index fe604b3c..05376a74 100644
--- a/tests/test_workbook.hpp
+++ b/tests/test_workbook.hpp
@@ -206,6 +206,6 @@ public:
         test_book.load(dest_filename);
         auto test_sheet = test_book.get_active_sheet();
 
-        TS_ASSERT_LESS_THAN_EQUALS(std::stod(test_sheet.get_cell("A1").get_value()) - float_value, 0.001);
+        TS_ASSERT_LESS_THAN_EQUALS(test_sheet.get_cell("A1").get_internal_value_numeric() - float_value, 0.00001);
     }
 };