Added test cases for TrappingRainWater

Dynamic-Programming/tests/TrappingRainWater.test.js

@@ -0,0 +1,11 @@
+import { trap } from '../TrappingRainWater'
+
+describe('TrappingRainWater', () => {
+  it('expects 6 units of rain water are being trapped', () => {
+    expect(trap([0,1,0,2,1,0,1,3,2,1,2,1])).toBe(6)
+  })
+
+  it('expects 9 units of rain water are being trapped', () => {
+    expect(trap([4,2,0,3,2,5])).toBe(9)
+  })
+})