added test

histogram.cpp

@@ -5,6 +5,8 @@ using namespace std;
 
 
 void find_minmax(const vector<double>& numbers, double& min, double& max) {
+    max = 0;
+    if (numbers.size() != 0) {
         min = numbers[0];
         max = numbers[0];
         for (auto el : numbers) {
@@ -15,6 +17,7 @@ void find_minmax(const vector<double>& numbers, double& min, double& max) {
                 min = el;
             }
         }
+    } else {min = 0;}
 }
 
 vector<size_t> make_histogram(const vector<double>& numbers, size_t bin_count) {

unittest.cpp

@@ -0,0 +1,36 @@
+#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("one element") {
+    double min = 0;
+    double max = 0;
+    find_minmax({ 1 }, min, max);
+    CHECK(min == 1);
+    CHECK(max == 1);
+}
+
+TEST_CASE("negative elements") {
+    double min = 0;
+    double max = 0;
+    find_minmax({ -81, 2 }, min, max);
+    CHECK(min == -81);
+    CHECK(max == 2);
+}