diff --git a/src/generics/lib.generics.ts b/src/generics/lib.generics.ts
index 4376a2d..f59534c 100644
--- a/src/generics/lib.generics.ts
+++ b/src/generics/lib.generics.ts
@@ -141,7 +141,7 @@ namespace __Array {
             end = this.length;
         }
 
-        for (let i = start; i <= end; i++)
+        for (let i = start; i < end; i++)
             newArray[i] = value;
 
         return newArray;
diff --git a/tests/array_fill.ts b/tests/array_fill.ts
index 4d9986d..bdef201 100644
--- a/tests/array_fill.ts
+++ b/tests/array_fill.ts
@@ -2,14 +2,27 @@ function main() {
     const array1 = [1, 2, 3, 4];
 
     // Fill with 0 from position 2 until position 4
-    console.log(array1.fill(0, 2, 4));
+    const zeros = array1.fill(0, 2, 4);
+    console.log(zeros);
     // Expected output: Array [1, 2, 0, 0]
+    assert(zeros.length == 4 && zeros[0] == 1 && zeros[1] == 2 && zeros[2] == 0 && zeros[3] == 0);
 
     // Fill with 5 from position 1
-    console.log(array1.fill(5, 1));
+    const fives = array1.fill(5, 1);
+    console.log(fives);
     // Expected output: Array [1, 5, 5, 5]
+    assert(fives.length == 4 && fives[0] == 1 && fives[1] == 5 && fives[2] == 5 && fives[3] == 5);
 
-    console.log(array1.fill(6));
+    const sixes = array1.fill(6);
+    console.log(sixes);
     // Expected output: Array [6, 6, 6, 6]
+    assert(sixes.length == 4 && sixes[0] == 6 && sixes[1] == 6 && sixes[2] == 6 && sixes[3] == 6);
+
+    // `end` is not filled: this wrote one past it, and past the end of the array when `end` is its length
+    const inner = [1, 2, 3].fill(9, 1, 2);
+    console.log(inner);
+    // Expected output: Array [1, 9, 3]
+    assert(inner.length == 3 && inner[0] == 1 && inner[1] == 9 && inner[2] == 3);
+
     console.log("ALL DONE");
 }