added a functional test and optimized a test

tests/app.test.ts

@@ -166,7 +166,6 @@ describe("POST /images works properly", () => {
   });
 
   it("should return 400 for malformed requests", async () => {
-    mock.restore();
     const res = await request(app)
       .post("/images")
       .set("authorization", `Bearer ${token}`)
@@ -180,17 +179,22 @@ describe("POST /images works properly", () => {
 });
 
 describe("GET /images/<id> works properly", () => {
+  let id: string;
+  let list: Image[];
+  beforeAll(async () => {
+    const res = await request(app).get("/images");
+    list = res.body.images;
+    id = list[0]._id;
+  });
+
   it("should return 200 for existing ids", async () => {
-    const list = await request(app).get("/images");
-    const id = list.body.images[0]._id;
     const res = await request(app).get(`/images/${id}`);
     expect(res.status).toBe(200);
   });
 
   it("should return 404 for non-existing ids", async () => {
-    const list = await request(app).get("/images");
     const id = "000000000000000000000000"; // this was the least posible to exist ID
-    if (!(id in list.body.images)) {
+    if (!(id in list)) {
       const res = await request(app).get(`/images/${id}`);
       expect(res.status).toBe(404);
     }
@@ -286,4 +290,23 @@ describe("PUT /images/<id> works properly", () => {
       .send({ status: "available" });
     expect(res.status).toBe(403);
   });
+
+  it("should have its changes be reflected onto the DB", async () => {
+    const image = await request(app)
+    .post("/images")
+    .set("authorization", `Bearer ${token}`)
+    .send({
+      url: "https://test.url.com/5",
+      status: "available",
+      tags: ["2girls", "touhou"],
+    });
+    const id = image.body.image._id;
+    await request(app)
+    .put(`/images/${id}`)
+    .set("authorization", `Bearer ${token}`)
+    .send({ status: "consumed" });
+    
+    const res = await request(app).get(`/images/${id}`);
+    expect(res.body.image).toHaveProperty("status", "consumed");
+  })
 });