diff --git a/.DS_Store b/.DS_Store
new file mode 100644
index 00000000..c2261ba5
Binary files /dev/null and b/.DS_Store differ
diff --git a/index.js b/index.js
index 0f4b28b4..70f29616 100644
--- a/index.js
+++ b/index.js
@@ -1,17 +1,45 @@
 class SortedList {
-  constructor() {}
+  constructor() {
+    this.items = [];
+    this.length = 0;
+  }
 
-  add(item) {}
+  add(item) {
+    this.items.push(item);
+    this.items.sort((a,b) => a - b);
+    this.length = this.items.length;
+  }
 
-  get(pos) {}
+  get(pos) {
+    if (pos < 0 || pos >= this.length) {
+      throw new Error ("OutOfBounds");
+    }
+    return this.items[pos];
+  }
 
-  max() {}
+  max() {
+    if (this.length === 0) {
+      throw new Error ("EmptySortedList");
+    }
+    return this.items[this.length - 1];
+  }
 
-  min() {}
+  min() {
+    if (this.length === 0) {
+      throw new Error ("EmptySortedList")
+    }
+    return this.items[0];
+  }
 
   sum() {}
 
-  avg() {}
+  avg() {
+    if (this.length === 0) {
+      throw new Error ("EmptySortedList");
+    }
+    const total = this.sum();
+    return total / this.length;
+  } 
 }
 
 module.exports = SortedList;
diff --git a/package.json b/package.json
index 3a5127ae..2e1f0a9d 100644
--- a/package.json
+++ b/package.json
@@ -19,5 +19,9 @@
     "intro"
   ],
   "author": "fer@ironhack.com",
-  "license": "MIT"
+  "license": "MIT",
+  "devDependencies": {
+    "chai": "^6.2.1",
+    "mocha": "^11.7.5"
+  }
 }