diff --git a/src/data-structures/tree/fenwick-tree/FenwickTree.js b/src/data-structures/tree/fenwick-tree/FenwickTree.js
index da4f8416..7bfb8426 100644
--- a/src/data-structures/tree/fenwick-tree/FenwickTree.js
+++ b/src/data-structures/tree/fenwick-tree/FenwickTree.js
@@ -13,13 +13,13 @@ export default class FenwickTree {
   }
 
   /**
-   * Adds value to position.
+   * Adds value to existing value at position.
    *
    * @param  {number} position
    * @param  {number} value
    * @return {FenwickTree}
    */
-  update(position, value) {
+  increase(position, value) {
     if (position < 1 || position > this.arraySize) {
       throw new Error('Position is out of allowed range');
     }
diff --git a/src/data-structures/tree/fenwick-tree/__test__/FenwickTree.test.js b/src/data-structures/tree/fenwick-tree/__test__/FenwickTree.test.js
index ece00ec8..0fd71657 100644
--- a/src/data-structures/tree/fenwick-tree/__test__/FenwickTree.test.js
+++ b/src/data-structures/tree/fenwick-tree/__test__/FenwickTree.test.js
@@ -20,7 +20,7 @@ describe('FenwickTree', () => {
     expect(tree.treeArray.length).toBe(inputArray.length + 1);
 
     inputArray.forEach((value, index) => {
-      tree.update(index + 1, value);
+      tree.increase(index + 1, value);
     });
 
     expect(tree.treeArray).toEqual([0, 3, 5, -1, 10, 5, 9, -3, 19, 7, 9, 3]);
@@ -41,23 +41,42 @@ describe('FenwickTree', () => {
     expect(tree.queryRange(1, 2)).toBe(5);
     expect(tree.queryRange(2, 4)).toBe(7);
     expect(tree.queryRange(6, 9)).toBe(11);
+
+    tree.increase(3, 1);
+
+    expect(tree.query(1)).toBe(3);
+    expect(tree.query(2)).toBe(5);
+    expect(tree.query(3)).toBe(5);
+    expect(tree.query(4)).toBe(11);
+    expect(tree.query(5)).toBe(16);
+    expect(tree.query(6)).toBe(20);
+    expect(tree.query(7)).toBe(17);
+    expect(tree.query(8)).toBe(20);
+    expect(tree.query(9)).toBe(27);
+    expect(tree.query(10)).toBe(29);
+    expect(tree.query(11)).toBe(32);
+
+    expect(tree.queryRange(1, 1)).toBe(3);
+    expect(tree.queryRange(1, 2)).toBe(5);
+    expect(tree.queryRange(2, 4)).toBe(8);
+    expect(tree.queryRange(6, 9)).toBe(11);
   });
 
   it('should correctly execute queries', () => {
     const tree = new FenwickTree(5);
 
-    tree.update(1, 4);
-    tree.update(3, 7);
+    tree.increase(1, 4);
+    tree.increase(3, 7);
 
     expect(tree.query(1)).toBe(4);
     expect(tree.query(3)).toBe(11);
     expect(tree.query(5)).toBe(11);
     expect(tree.queryRange(2, 3)).toBe(7);
 
-    tree.update(2, 5);
+    tree.increase(2, 5);
     expect(tree.query(5)).toBe(16);
 
-    tree.update(1, 3);
+    tree.increase(1, 3);
     expect(tree.queryRange(1, 1)).toBe(7);
     expect(tree.query(5)).toBe(19);
     expect(tree.queryRange(1, 5)).toBe(19);
@@ -66,12 +85,12 @@ describe('FenwickTree', () => {
   it('should throw exceptions', () => {
     const tree = new FenwickTree(5);
 
-    const updateAtInvalidLowIndex = () => {
-      tree.update(0, 1);
+    const increaseAtInvalidLowIndex = () => {
+      tree.increase(0, 1);
     };
 
-    const updateAtInvalidHighIndex = () => {
-      tree.update(10, 1);
+    const increaseAtInvalidHighIndex = () => {
+      tree.increase(10, 1);
     };
 
     const queryInvalidLowIndex = () => {
@@ -86,8 +105,8 @@ describe('FenwickTree', () => {
       tree.queryRange(3, 2);
     };
 
-    expect(updateAtInvalidLowIndex).toThrowError();
-    expect(updateAtInvalidHighIndex).toThrowError();
+    expect(increaseAtInvalidLowIndex).toThrowError();
+    expect(increaseAtInvalidHighIndex).toThrowError();
     expect(queryInvalidLowIndex).toThrowError();
     expect(queryInvalidHighIndex).toThrowError();
     expect(rangeQueryInvalidIndex).toThrowError();