add contains method to NumberRange

Author: kaiosilveira

src/number-range/index.js

@@ -10,6 +10,10 @@ class NumberRange {
   get max() {
     return this._data.max;
   }
+
+  contains(n) {
+    return n >= this.min && n <= this.max;
+  }
 }
 
 module.exports = { NumberRange };

src/number-range/index.test.js

@@ -1,13 +1,36 @@
 const { NumberRange } = require('.');
 
 describe('NumberRange', () => {
-  it('should have a min and a max', () => {
-    const min = 10;
-    const max = 20;
+  const min = 10;
+  const max = 20;
 
+  it('should have a min and a max', () => {
     const range = new NumberRange(min, max);
 
     expect(range.min).toEqual(min);
     expect(range.max).toEqual(max);
   });
+
+  describe('contains', () => {
+    it('should return true if a number falls inside of the specified range', () => {
+      const range = new NumberRange(min, max);
+      expect(range.contains(15)).toEqual(true);
+    });
+
+    it('should return false if a number falls outside of the specified range', () => {
+      const range = new NumberRange(min, max);
+      expect(range.contains(9)).toEqual(false);
+      expect(range.contains(21)).toEqual(false);
+    });
+
+    it('should contain the lower end of the range', () => {
+      const range = new NumberRange(min, max);
+      expect(range.contains(min)).toEqual(true);
+    });
+
+    it('should contain the upper end of the range', () => {
+      const range = new NumberRange(min, max);
+      expect(range.contains(max)).toEqual(true);
+    });
+  });
 });