code: реализован unittest с большим количеством случаев

histogram.cpp

@@ -1,7 +1,13 @@
 #include "histogram.h"
 #include <vector>
 
-void find_minmax(const std::vector <double> &numbers, double &min, double &max){
+void find_minmax(const std::vector <double> &numbers, double &min, double &max, bool &res ){
+
+    if (numbers.size()==0){
+        res = true;
+        return;
+    }
+
     min = numbers[0];
     max = numbers[0];
     for ( double x : numbers ){
@@ -14,9 +20,9 @@ void find_minmax(const std::vector <double> &numbers, double &min, double &max){
 }
 
 std::vector<std::size_t> make_histogram(const std::vector<double> &numbers, std::size_t bin_count) {
-    double min = numbers[0];
-    double max = numbers[0];
-    find_minmax(numbers, min, max);
+    double min, max;
+    bool res = false;
+    find_minmax(numbers, min, max, res);
     double bin_size = ( max - min ) / bin_count;
     std::vector<std::size_t> bins ( bin_count );
     for (std::size_t i=0; i <  numbers.size(); i++ ){

histogram_internal.h

@@ -3,6 +3,6 @@
 
 #include <vector>
 
-void find_minmax(const std::vector <double> &numbers, double &min, double &max)
+void find_minmax(const std::vector <double> &numbers, double &min, double &max, bool &res);
 
 #endif // HISTOGRAM_INTERNAL_H_INCLUDED

text.cpp

@@ -6,6 +6,7 @@ const std::size_t SCREEN_WIDTH = 80;
 const std::size_t MAX_ASTERISK = SCREEN_WIDTH - 3 - 1;
 
 void show_histogram_text(const std::vector<std::size_t> &bins){
+    std::cout<<std::endl;
     std::size_t maxbin = bins[0];
     for (std::size_t i=1; i < bins.size(); i++){
         if (maxbin < bins[i]){

unittest.cpp

@@ -0,0 +1,67 @@
+#define DOCTEST_CONFIG_NO_MULTITHREADING
+#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
+#include "doctest.h"
+#include "histogram_internal.h"
+
+
+
+TEST_CASE("distinct positive numbers") {
+    bool res = false;
+    double min = 0;
+    double max = 0;
+    find_minmax({1, 2}, min, max, res);
+    CHECK(min == 1);
+    CHECK(max == 2);
+    CHECK(res==0);
+}
+
+TEST_CASE("negative numbers") {
+    bool res = false;
+    double min = 0;
+    double max = 0;
+    find_minmax({-1, -2}, min, max, res);
+    CHECK(min == -2);
+    CHECK(max == -1);
+    CHECK(res==0);
+}
+
+TEST_CASE("empty array") {
+    bool res = false;
+    double min = 0;
+    double max = 0;
+    std::vector<double> numbers;
+    find_minmax(numbers, min, max, res);
+    CHECK(min == 0);
+    CHECK(max == 0);
+    CHECK(res==1);
+}
+
+TEST_CASE("1 number") {
+    bool res = false;
+    double min = 0;
+    double max = 0;
+    find_minmax({-1}, min, max, res);
+    CHECK(min == -1);
+    CHECK(max == -1);
+    CHECK(res==0);
+}
+
+TEST_CASE("same number") {
+    bool res = false;
+    double min = 0;
+    double max = 0;
+    find_minmax({1,1,1,1}, min, max, res);
+    CHECK(min == 1);
+    CHECK(max == 1);
+    CHECK(res==0);
+}
+
+TEST_CASE("same number but zero") {
+    bool res = false;
+    double min = 0;
+    double max = 0;
+    find_minmax({0,0,0,0}, min, max, res);
+    CHECK(min == 0);
+    CHECK(max == 0);
+    CHECK(res==0);
+}