diff --git a/histogram.cpp b/histogram.cpp
new file mode 100644
index 0000000..3fa3cf2
--- /dev/null
+++ b/histogram.cpp
@@ -0,0 +1,35 @@
+#include "histogram.h"
+bool
+find_minmax(const std::vector<double>& numbers, double& min, double& max) {
+    min = numbers[0];
+    max = numbers[0];
+    for(double x : numbers){
+        if(x<min){
+            min=x;
+        }
+        if(x>max){
+            max=x;
+        }
+    }
+}
+std::vector<size_t>
+make_histogram(const std::vector<double>& numbers,size_t bin_count){
+    std::vector<size_t> bins(bin_count);
+    double min,max;
+    find_minmax(numbers,min,max);
+    double bin_size=(max-min)/bin_count;
+    for(size_t i=0; i<numbers.size(); i++){
+        bool found = false;
+        for(size_t j=0;(j<bin_count-1)&& !found; j++){
+            auto lo=min+j*bin_size;
+            auto hi=min+(j+1)*bin_size;
+            if((lo<=numbers[i])&&(numbers[i]<hi)){
+                bins[j]++;
+                found=true;
+            }
+        }if(!found){
+            bins[bin_count-1]++;
+        }
+    }
+    return bins;
+}
diff --git a/histogram_internal.h b/histogram_internal.h
new file mode 100644
index 0000000..56f34af
--- /dev/null
+++ b/histogram_internal.h
@@ -0,0 +1,8 @@
+#ifndef HISTOGRAM_INTERNAL_H_INCLUDED
+#define HISTOGRAM_INTERNAL_H_INCLUDED
+#include <vector>
+#include <iostream>
+bool
+find_minmax(const std::vector<double>& numbers, double& min, double& max);
+
+#endif
diff --git a/unittest.cpp b/unittest.cpp
new file mode 100644
index 0000000..e130618
--- /dev/null
+++ b/unittest.cpp
@@ -0,0 +1,38 @@
+#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({2, 2}, min, max);
+    CHECK(min == 2);
+    CHECK(max == 2);
+}
+TEST_CASE("empty vector"){
+    double min = 0;
+    double max = 0;
+    CHECK(!find_minmax({}, min, max));
+}
+TEST_CASE("vector of one elements"){
+    double min = 0;
+    double max = 0;
+    find_minmax({3}, min, max);
+    CHECK(min == max);
+}
+TEST_CASE("distinct negative numbers"){
+    double min = 0;
+    double max = 0;
+    find_minmax({-1, -2}, min, max);
+    CHECK(min == -2);
+    CHECK(max == -1);
+}
+TEST_CASE("vector of the same elements"){
+    double min = 0;
+    double max = 0;
+    find_minmax({3,3,3}, min, max);
+    CHECK(min == 3);
+    CHECK(max == 3);
+}
+