diff --git a/index.js b/index.js
index 0f4b28b4..8e2c02e2 100644
--- a/index.js
+++ b/index.js
@@ -1,17 +1,64 @@
 class SortedList {
-  constructor() {}
+  constructor() {
+    this.items = [];
+    this.length = this.items.length;
+  }
 
-  add(item) {}
+  add(item) {
+    this.items.push(item);
+    if (this.length > 1) {
+      this.length = this.items.length;
+      return this.items.sort((a, b) => a - b);
+    } else {
+      this.length = this.items.length;
+      return this.items;
+    }
+  }
 
-  get(pos) {}
+  get(pos) {
+    if (pos > this.length) {
+      throw new Error('OutOfBounds');
+    } else {
+      return this.items[pos];
+    }
+  }
 
-  max() {}
+  max() {
+    if (this.length === 0) {
+      throw new Error('EmptySortedList');
+    } else {
+      return Math.max(...this.items);
+    }
+  }
 
-  min() {}
+  min() {
+    if (this.length === 0) {
+      throw new Error('EmptySortedList');
+    } else {
+      return Math.min(...this.items);
+    }
+  }
 
-  sum() {}
+  sum() {
+    if (this.length === 0) {
+      return 0;
+    } else {
+      return this.items.reduce((sum, val) => {
+        return (sum += val);
+      });
+    }
+  }
 
-  avg() {}
+  avg() {
+    if (this.length === 0) {
+      throw new Error('EmptySortedList');
+    } else {
+      const total = this.items.reduce((sum, val) => {
+        return (sum += val);
+      });
+      return total / this.length;
+    }
+  }
 }
 
 module.exports = SortedList;
diff --git a/package.json b/package.json
index 3a5127ae..932523a5 100644
--- a/package.json
+++ b/package.json
@@ -19,5 +19,8 @@
     "intro"
   ],
   "author": "fer@ironhack.com",
-  "license": "MIT"
+  "license": "MIT",
+  "dependencies": {
+    "mocha": "^11.1.0"
+  }
 }