diff --git a/__tests__/Functions__Test.re b/__tests__/Functions__Test.re
index d5cc0d03..d32f44e8 100644
--- a/__tests__/Functions__Test.re
+++ b/__tests__/Functions__Test.re
@@ -69,4 +69,22 @@ describe("Functions", () => {
   test("max#3", () => {
     expect(Functions.max([|(-1.), (-2.), 0., (-2.2)|])) |> toEqual(0.)
   });
+  test("random#1", () => {
+    expect(Functions.random(1, 5)) |> toBeLessThanOrEqual(5)
+  });
+  test("random#2", () => {
+    expect(Functions.random(1, 5)) |> toBeGreaterThanOrEqual(1)
+  });
+  test("up#1", () => {
+    expect(Functions.up(1, 5)) |> toEqual([|1, 2, 3, 4, 5|])
+  });
+  test("up#2", () => {
+    expect(Functions.up(-1, 5)) |> toEqual([|(-1), 0, 1, 2, 3, 4, 5|])
+  });
+  test("down#1", () => {
+    expect(Functions.down(5, 1)) |> toEqual([|5, 4, 3, 2, 1|])
+  });
+  test("down#2", () => {
+    expect(Functions.down(5, -1)) |> toEqual([|5, 4, 3, 2, 1, 0, (-1)|])
+  });
 });
diff --git a/src/utility/lib/Functions.re b/src/utility/lib/Functions.re
index 4600f237..26a8bf20 100644
--- a/src/utility/lib/Functions.re
+++ b/src/utility/lib/Functions.re
@@ -13,8 +13,9 @@ let sum = Belt.Array.reduce(_, 0., (i, j) => i +. j);
 let mean = a => sum(a) /. (Array.length(a) |> float_of_int);
 let min = a => Belt.Array.reduce(a, a[0], (i, j) => i < j ? i : j);
 let max = a => Belt.Array.reduce(a, a[0], (i, j) => i > j ? i : j);
-let up = (a, b) => Array.make(b - a, a) |> Array.mapi((i, c) => c + i);
-let down = (a, b) => Array.make(a - b, a) |> Array.mapi((i, c) => c - i);
+let up = (a, b) => Array.make(b - a + 1, a) |> Array.mapi((i, c) => c + i);
+let down = (a, b) =>
+  Array.make(a - b + 1, a) |> Array.mapi((i, c) => c - i);
 let range = (min: float, max: float, n: int): array(float) => {
   switch (n) {
   | 0 => [||]