diff --git a/__tests__/Functions__Test.re b/__tests__/Functions__Test.re
new file mode 100644
index 00000000..874a143d
--- /dev/null
+++ b/__tests__/Functions__Test.re
@@ -0,0 +1,44 @@
+open Jest;
+open Expect;
+
+exception ShapeWrong(string);
+describe("Functions", () => {
+  test("interpolate", () => {
+    let a = Functions.interpolate(10., 20., 1., 2., 15.);
+    let b = 1.5;
+    expect(a) |> toEqual(b);
+  });
+  test("range#1", () => {
+    expect(Functions.range(1., 5., 3)) |> toEqual([|1., 3., 5.|])
+  });
+  test("range#2", () => {
+    expect(Functions.range(1., 5., 5)) |> toEqual([|1., 2., 3., 4., 5.|])
+  });
+  test("range#3", () => {
+    expect(Functions.range(-10., 15., 2)) |> toEqual([|(-10.), 15.|])
+  });
+  test("range#4", () => {
+    expect(Functions.range(-10., 15., 3)) |> toEqual([|(-10.), 2.5, 15.|])
+  });
+  test("range#5", () => {
+    expect(Functions.range(-10.3, 17., 3))
+    |> toEqual([|(-10.3), 3.3499999999999996, 17.|])
+  });
+  test("range#6", () => {
+    expect(Functions.range(-10.3, 17., 5))
+    |> toEqual([|
+         (-10.3),
+         (-3.4750000000000005),
+         3.3499999999999996,
+         10.175,
+         17.0,
+       |])
+  });
+  test("range#7", () => {
+    expect(Functions.range(-10.3, 17.31, 3))
+    |> toEqual([|(-10.3), 3.504999999999999, 17.31|])
+  });
+  test("range#8", () => {
+    expect(Functions.range(1., 1., 3)) |> toEqual([|1., 1., 1.|])
+  });
+});
diff --git a/src/utility/lib/Functions.re b/src/utility/lib/Functions.re
index a887be60..a2e4ba66 100644
--- a/src/utility/lib/Functions.re
+++ b/src/utility/lib/Functions.re
@@ -24,7 +24,8 @@ let range = (min: float, max: float, n: int): array(float) => {
   | _ when n < 0 => raise(RangeWrong("n is less then zero"))
   | _ when min > max => raise(RangeWrong("Min values is less then max"))
   | _ =>
-    let diff = max -. min;
-    Belt.Array.makeBy(n, i => float_of_int(i) *. diff);
+    let diff = (max -. min) /. Belt.Float.fromInt(n - 1);
+    Belt.Array.makeBy(n, i => {min +. Belt.Float.fromInt(i) *. diff});
   };
 };
+let random = Js.Math.random_int;
diff --git a/src/utility/lib/functions.js b/src/utility/lib/functions.js
index a4353e52..c8c6fbfa 100644
--- a/src/utility/lib/functions.js
+++ b/src/utility/lib/functions.js
@@ -100,6 +100,7 @@ function max(arr) {
 }
 
 /**
+ * @Done
  * @param {number} min
  * @param {number} max
  * @return {number}