wrote the function for dedupe and wrote test cases for it to pass the acceptance criteria

Author: fayaz551

Sprint-1/implement/dedupe.js

@@ -1 +1,14 @@
-function dedupe() {}
+function dedupe(arr) {
+  if (!Array.isArray(arr)) return null; 
+
+  const seen = [];
+  
+  for (const item of arr) {
+    if (!seen.includes(item)) {
+      seen.push(item);
+    }
+  }
+
+  return seen;
+}
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -13,15 +13,31 @@ E.g. dedupe([1, 2, 1]) target output: [1, 2]
 
 // Acceptance Criteria:
 
-// Given an empty array
-// When passed to the dedupe function
-// Then it should return an empty array
-test.todo("given an empty array, it returns an empty array");
-
-// Given an array with no duplicates
-// When passed to the dedupe function
-// Then it should return a copy of the original array
-
-// Given an array with strings or numbers
-// When passed to the dedupe function
-// Then it should remove the duplicate values, preserving the first occurence of each element
+describe("dedupe", () => {
+  // Given an empty array
+  // When passed to the dedupe function
+  // Then it should return an empty array
+  test("given an empty array, it returns an empty array", () => {
+    expect(dedupe([])).toEqual([]);
+  });
+
+  // Given an array with no duplicates
+  // When passed to the dedupe function
+  // Then it should return a copy of the original array
+  test("returns a copy when no duplicates exist", () => {
+    const input = [1, 2, 3];
+    const output = dedupe(input);
+
+    expect(output).toEqual([1, 2, 3]);
+    expect(output).not.toBe(input); // ensures it's a new array, not the same reference
+  });
+
+  // Given an array with strings or numbers
+  // When passed to the dedupe function
+  // Then it should remove the duplicate values, preserving the first occurrence
+  test("removes duplicates and preserves first occurrence", () => {
+    expect(dedupe(['a','a','a','b','b','c'])).toEqual(['a','b','c']);
+    expect(dedupe([5, 1, 1, 2, 3, 2, 5, 8])).toEqual([5, 1, 2, 3, 8]);
+    expect(dedupe([1, 2, 1])).toEqual([1, 2]);
+  });
+});