пятый этап сделан, дошел до6го пункта

project/.gitignore

@@ -1,2 +1,4 @@
 /obj
 /bin
+/pr3.depend
+/pr3.layout

project/histogram_internal.h

@@ -1,7 +1,7 @@
-#ifndef FINDMINMAX_H_INCLUDED
-#define FINDMINMAX_H_INCLUDED
+#ifndef HISTOGRAM_INTERNAL_H_INCLUDED
+#define HISTOGRAM_INTERNAL_H_INCLUDED
 #include <vector>
 
-void find_minmax(vector<double> numbers, double& min, double& max);
+void find_minmax(std::vector<double> numbers, double& min, double& max);
 
-#endif // FINDMINMAX_H_INCLUDED
+#endif // HISTOGRAM_INTERNAL_H_INCLUDED

unittest.cpp

@@ -0,0 +1,41 @@
+#define DOCTEST_CONFIG_NO_MULTITHREADING
+#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
+#include "doctest.h"
+#include "project/histogram_internal.h"
+
+TEST_CASE("distinct positive numbers 1")
+{
+    double min = 0;
+    double max = 0;
+    find_minmax({1, 2}, min, max);
+    CHECK(min == 1);
+    CHECK(max == 2);
+}
+
+TEST_CASE("distinct positive numbers 2") {
+    double min = 0;
+    double max = 0;
+    std::vector<double>v{2,1};
+    CHECK(v.size() != 0);
+    CHECK(v.size() != 1);
+    find_minmax({1, 2}, min, max);
+    CHECK(min == 1);
+    CHECK(max == 2);
+    CHECK(min != max);
+}
+
+TEST_CASE("vector with one element") {
+    double min = 0;
+    double max = 0;
+    find_minmax({1}, min, max);
+    CHECK(min == 1);
+    CHECK(max == 1);
+}
+
+TEST_CASE("vector with same elements") {
+    double min = 0;
+    double max = 0;
+    find_minmax({2,2,2}, min, max);
+    CHECK(min == 2);
+    CHECK(max == 2);
+}