Добавил модули проверки

histogram.cpp

@@ -1,7 +1,8 @@
 #include <vector>
-#include "histogram.h"
+#include "histogram_internal.h"
 using namespace std;
 
+/*
 vector<size_t> make_histogram(const vector<double>& numbers, size_t bin_count) {
 
     vector<size_t> bins(bin_count);
@@ -42,9 +43,18 @@ vector<size_t> make_histogram(const vector<double>& numbers, size_t bin_count) {
         }
     }
     return bins;
-}
+} */
+
+bool find_minmax(const vector<double>& numbers, double& min, double& max) {
+    if (numbers.size() == 0) {
+        return false;
+    }
+    for (auto i = 0; i < numbers.size(); i++) {
+        if (
+            numbers[i] < 0
+            ) return false;
+    }
 
-void find_minmax(const vector<double>& numbers, double& min, double& max) {
     min = numbers[0];
     for (auto i = 0; i < numbers.size(); i++) {
         if (numbers[i] < min) {
@@ -58,5 +68,5 @@ void find_minmax(const vector<double>& numbers, double& min, double& max) {
             max = numbers[i];
         }
     }
-
+    return true;
 }

histogram_internal.h

@@ -1,4 +1,4 @@
 #pragma once
 #include <vector>
 
-void find_minmax(const  std::vector<double>& numbers, double& min, double& max);
+bool find_minmax(const  std::vector<double>& numbers, double& min, double& max);

unittest.cpp

@@ -0,0 +1,19 @@
+#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);
+
+    find_minmax({ 1 }, min, max);
+    CHECK(min == max);
+    CHECK(find_minmax({ -1 }, min, max) == false);
+    find_minmax({ 2, 2, 2, 2 }, min, max);
+    CHECK(min == max);
+
+}

unittest.vcxproj

@@ -17,7 +17,6 @@
       <Configuration>Release</Configuration>
       <Platform>x64</Platform>
     </ProjectConfiguration>
-
   </ItemGroup>
   <PropertyGroup Label="Globals">
     <VCProjectVersion>16.0</VCProjectVersion>
@@ -53,11 +52,10 @@
     <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.$(Platform).user.props')" Label="LocalAppDataPlatform" />
@@ -71,9 +69,7 @@
   <ImportGroup Label="PropertySheets" Condition="'$(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)|$(Platform)'=='Debug|Win32'">
     <ClCompile>
       <WarningLevel>Level3</WarningLevel>
@@ -130,8 +126,13 @@
       <GenerateDebugInformation>true</GenerateDebugInformation>
     </Link>
   </ItemDefinitionGroup>
-
+  <ItemGroup>
-  <ItemGroup></ItemGroup>
+    <ClCompile Include="histogram.cpp" />
+    <ClCompile Include="unittest.cpp" />
+  </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="histogram_internal.h" />
+  </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>

unittest.vcxproj.filters

@@ -14,4 +14,17 @@
       <Extensions>rc;ico;cur;bmp;dlg;rc2;rct;bin;rgs;gif;jpg;jpeg;jpe;resx;tiff;tif;png;wav;mfcribbon-ms</Extensions>
     </Filter>
   </ItemGroup>
+  <ItemGroup>
+    <ClCompile Include="unittest.cpp">
+      <Filter>Исходные файлы</Filter>
+    </ClCompile>
+    <ClCompile Include="histogram.cpp">
+      <Filter>Исходные файлы</Filter>
+    </ClCompile>
+  </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="histogram_internal.h">
+      <Filter>Исходные файлы</Filter>
+    </ClInclude>
+  </ItemGroup>
 </Project>