added tests

histogram.cpp

@@ -4,19 +4,19 @@ using namespace std;
 
 void find_minmax(const vector<double> &numbers, double &min, double &max)
 {
-    min = numbers[0];
-    max = numbers[0];
-    for (auto el : numbers)
-    {
-        if (el > max)
-        {
-            max = el;
-        }
-        if (el < min)
-        {
-            min = el;
+    max = 0;
+    if (numbers.size() != 0) {
+        min = numbers[0];
+        max = numbers[0];
+        for (auto el : numbers) {
+            if (el > max) {
+                max = el;
+            }
+            if (el < min) {
+                min = el;
+            }
         }
-    }
+    } else {min = 0;}
 }
 
 vector<size_t> make_histogram(const vector<double> &numbers, const size_t bin_count){

histogram_internal.h

@@ -0,0 +1,4 @@
+#pragma once
+#include <vector>
+
+void find_minmax(const std::vector<double> &numbers, double &min, double &max);

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);
+}