From 2ee96f7713dbeed853b2679736444e64eebd8b76 Mon Sep 17 00:00:00 2001
From: Alex Banna <alexanderbanna@gmail.com>
Date: Sat, 28 Mar 2026 14:31:13 -0500
Subject: [PATCH] test(items): add dedicated GET /items/:id endpoint tests

- Existing item returns 200 with correct JSON (id, name, description, inserted_at)
- Response body has exactly the 4 expected fields
- id is integer, inserted_at is valid ISO 8601 datetime
- Non-existent id returns 404 with exact error message
- Non-integer id (abc) returns 404, not 500
- Float-like id (1.5), negative id (-1), and zero id (0) return 404
- Content-Type is application/json on both 200 and 404 responses
- Correct item returned when multiple items exist
- Unsupported methods (PUT, PATCH, POST) on /items/:id return 404
- Default empty description verified via direct Repo insert

Implements: HAR-581
---
 test/items_api/get_item_test.exs | 148 +++++++++++++++++++++++++++++++
 1 file changed, 148 insertions(+)
 create mode 100644 test/items_api/get_item_test.exs

diff --git a/test/items_api/get_item_test.exs b/test/items_api/get_item_test.exs
new file mode 100644
index 0000000..fdc02d0
--- /dev/null
+++ b/test/items_api/get_item_test.exs
@@ -0,0 +1,148 @@
+defmodule ItemsApi.GetItemTest do
+  use ExUnit.Case, async: false
+
+  setup do
+    :ok = Ecto.Adapters.SQL.Sandbox.checkout(ItemsApi.Repo)
+    :ok
+  end
+
+  defp call(conn) do
+    ItemsApi.Router.call(conn, ItemsApi.Router.init([]))
+  end
+
+  defp json_response(conn) do
+    Jason.decode!(conn.resp_body)
+  end
+
+  defp create_item(attrs \\ %{}) do
+    default = %{"name" => "Test Item", "description" => "A test item"}
+    changeset = ItemsApi.Item.changeset(%ItemsApi.Item{}, Map.merge(default, attrs))
+    {:ok, item} = ItemsApi.Repo.insert(changeset)
+    item
+  end
+
+  describe "GET /items/:id" do
+    test "returns HTTP 200 for existing item" do
+      item = create_item()
+      conn = Plug.Test.conn(:get, "/items/#{item.id}") |> call()
+
+      assert conn.status == 200
+    end
+
+    test "returns item with correct JSON body" do
+      item = create_item(%{"name" => "Widget", "description" => "A fine widget"})
+      conn = Plug.Test.conn(:get, "/items/#{item.id}") |> call()
+
+      resp = json_response(conn)
+      assert resp["id"] == item.id
+      assert resp["name"] == "Widget"
+      assert resp["description"] == "A fine widget"
+      assert resp["inserted_at"] != nil
+    end
+
+    test "response body contains exactly id, name, description, inserted_at" do
+      item = create_item()
+      conn = Plug.Test.conn(:get, "/items/#{item.id}") |> call()
+
+      resp = json_response(conn)
+      assert Map.keys(resp) |> Enum.sort() == ["description", "id", "inserted_at", "name"]
+    end
+
+    test "id is an integer" do
+      item = create_item()
+      conn = Plug.Test.conn(:get, "/items/#{item.id}") |> call()
+
+      assert is_integer(json_response(conn)["id"])
+    end
+
+    test "inserted_at is a valid ISO 8601 datetime string" do
+      item = create_item()
+      conn = Plug.Test.conn(:get, "/items/#{item.id}") |> call()
+
+      inserted_at = json_response(conn)["inserted_at"]
+      assert is_binary(inserted_at)
+      assert {:ok, _dt, _offset} = DateTime.from_iso8601(inserted_at)
+    end
+
+    test "returns item with default empty description" do
+      changeset = ItemsApi.Item.changeset(%ItemsApi.Item{}, %{"name" => "No Desc"})
+      {:ok, item} = ItemsApi.Repo.insert(changeset)
+      conn = Plug.Test.conn(:get, "/items/#{item.id}") |> call()
+
+      assert json_response(conn)["description"] == ""
+    end
+
+    test "sets Content-Type to application/json" do
+      item = create_item()
+      conn = Plug.Test.conn(:get, "/items/#{item.id}") |> call()
+
+      assert Plug.Conn.get_resp_header(conn, "content-type") == ["application/json"]
+    end
+
+    test "returns HTTP 404 for non-existent id" do
+      conn = Plug.Test.conn(:get, "/items/9999") |> call()
+
+      assert conn.status == 404
+    end
+
+    test "returns exact error message for non-existent id" do
+      conn = Plug.Test.conn(:get, "/items/9999") |> call()
+
+      assert json_response(conn) == %{"error" => "item not found"}
+    end
+
+    test "returns 404 with error for non-integer id" do
+      conn = Plug.Test.conn(:get, "/items/abc") |> call()
+
+      assert conn.status == 404
+      assert json_response(conn) == %{"error" => "item not found"}
+    end
+
+    test "returns 404 for float-like id" do
+      conn = Plug.Test.conn(:get, "/items/1.5") |> call()
+
+      assert conn.status == 404
+      assert json_response(conn) == %{"error" => "item not found"}
+    end
+
+    test "returns 404 for negative id" do
+      conn = Plug.Test.conn(:get, "/items/-1") |> call()
+
+      assert conn.status == 404
+      assert json_response(conn) == %{"error" => "item not found"}
+    end
+
+    test "returns 404 for zero id" do
+      conn = Plug.Test.conn(:get, "/items/0") |> call()
+
+      assert conn.status == 404
+      assert json_response(conn) == %{"error" => "item not found"}
+    end
+
+    test "404 response sets Content-Type to application/json" do
+      conn = Plug.Test.conn(:get, "/items/9999") |> call()
+
+      assert Plug.Conn.get_resp_header(conn, "content-type") == ["application/json"]
+    end
+
+    test "returns correct item when multiple exist" do
+      _first = create_item(%{"name" => "First"})
+      second = create_item(%{"name" => "Second"})
+      _third = create_item(%{"name" => "Third"})
+
+      conn = Plug.Test.conn(:get, "/items/#{second.id}") |> call()
+
+      assert conn.status == 200
+      assert json_response(conn)["name"] == "Second"
+    end
+
+    test "unsupported methods on /items/:id return 404" do
+      item = create_item()
+
+      for method <- [:put, :patch, :post] do
+        conn = Plug.Test.conn(method, "/items/#{item.id}") |> call()
+        assert conn.status == 404, "Expected 404 for #{method |> to_string() |> String.upcase()} /items/#{item.id}"
+      end
+    end
+  end
+end