diff --git a/histogram.cpp b/histogram.cpp
index 9eec184..eb2de5e 100644
--- a/histogram.cpp
+++ b/histogram.cpp
@@ -5,17 +5,20 @@
 using namespace std;
 
 void find_minmax(const vector<double>& numbers, double& min, double& max) {
-    min = numbers[0];
-    max = numbers[0];
-    for (double x : numbers)
+    if (numbers.size() == 2)
     {
-        if (x < min)
+        min = numbers[0];
+        max = numbers[0];
+        for (double x : numbers)
         {
-            min = x;
-        }
-        if (x > max)
-        {
-            max = x;
+            if (x < min)
+            {
+                min = x;
+            }
+            if (x > max)
+            {
+                max = x;
+            }
         }
     }
 }
diff --git a/unittest.cpp b/unittest.cpp
index e69de29..485d693 100644
--- a/unittest.cpp
+++ b/unittest.cpp
@@ -0,0 +1,27 @@
+#define DOCTEST_CONFIG_NO_MULTITHREADING
+#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
+#include "doctest.h"
+#include "histogram_internal.h"
+
+TEST_CASE("distinct positive numbers") {
+    double min = 0;
+    double max = 0;
+    find_minmax({ 1, 2 }, min, max);
+    CHECK(min == 1);
+    CHECK(max == 2);
+}
+
+TEST_CASE("empty vector") {
+    double min = 0;
+    double max = 0;
+    find_minmax({}, min, max);
+    CHECK(min == 0);
+    CHECK(max == 0);
+}
+TEST_CASE("negative values") {
+    double min = 0;
+    double max = 0;
+    find_minmax({-2, -4}, min, max);
+    CHECK(min == -4);
+    CHECK(max == -2);
+}
\ No newline at end of file
diff --git a/unittest.vcxproj b/unittest.vcxproj
index aee391f..3e22914 100644
--- a/unittest.vcxproj
+++ b/unittest.vcxproj
@@ -17,7 +17,6 @@
       <Configuration>Release</Configuration>
       <Platform>x64</Platform>
     </ProjectConfiguration>
-
   </ItemGroup>
   <PropertyGroup Label="Globals">
     <VCProjectVersion>17.0</VCProjectVersion>
@@ -53,27 +52,24 @@
     <WholeProgramOptimization>true</WholeProgramOptimization>
     <CharacterSet>Unicode</CharacterSet>
   </PropertyGroup>
-
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   <ImportGroup Label="ExtensionSettings">
   </ImportGroup>
-  <ImportGroup Label="Shared" >
+  <ImportGroup Label="Shared">
+  </ImportGroup>
+  <ImportGroup Label="PropertySheets" Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+  </ImportGroup>
+  <ImportGroup Label="PropertySheets" Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+  </ImportGroup>
+  <ImportGroup Label="PropertySheets" Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+  </ImportGroup>
+  <ImportGroup Label="PropertySheets" Condition="'$(Configuration)|$(Platform)'=='Release|x64'">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
   </ImportGroup>
-    <ImportGroup Label="PropertySheets" Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
-      <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
-    </ImportGroup>
-    <ImportGroup Label="PropertySheets" Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
-      <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
-    </ImportGroup>
-    <ImportGroup Label="PropertySheets" Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
-      <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
-    </ImportGroup>
-    <ImportGroup Label="PropertySheets" Condition="'$(Configuration)|$(Platform)'=='Release|x64'">
-      <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
-    </ImportGroup>
-
   <PropertyGroup Label="UserMacros" />
-
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
     <ClCompile>
       <WarningLevel>Level3</WarningLevel>
@@ -130,9 +126,15 @@
       <GenerateDebugInformation>true</GenerateDebugInformation>
     </Link>
   </ItemDefinitionGroup>
-
-  <ItemGroup></ItemGroup>
+  <ItemGroup>
+    <ClCompile Include="histogram.cpp" />
+    <ClCompile Include="unittest.cpp" />
+  </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="doctest.h" />
+    <ClInclude Include="histogram_internal.h" />
+  </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
-</Project>
+</Project>
\ No newline at end of file