diff --git a/unittest.cpp b/unittest.cpp
new file mode 100644
index 0000000..7d95ded
--- /dev/null
+++ b/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("distinct negative numbers") {
+    double min = 0;
+    double max = 0;
+    find_minmax({-1, -2}, min, max);
+    CHECK(min == -2);
+    CHECK(max == -1);
+}
+
+TEST_CASE("one element") {
+    double min = 0;
+    double max = 0;
+    find_minmax({1}, min, max);
+    CHECK(min == 1);
+    CHECK(max == 1);
+}
+
+TEST_CASE("same numbers") {
+    double min = 0;
+    double max = 0;
+    find_minmax({1, 1}, min, max);
+    CHECK(min == 1);
+    CHECK(max == 1);
+}