add tests

test/feed_reader/temp_file_test.exs

@@ -0,0 +1,26 @@
+defmodule FeedReader.TempFileTest do
+  use ExUnit.Case, async: true
+
+  alias FeedReader.TempFile
+
+  test "returns a path in the system temporary directory" do
+    path = TempFile.random_file()
+
+    assert Path.dirname(path) == System.tmp_dir!()
+    assert Path.extname(path) == ".xml"
+    assert String.starts_with?(Path.basename(path), "feed_reader-")
+  end
+
+  test "uses the supplied base name" do
+    path = TempFile.random_file("download")
+
+    assert Path.basename(path) =~ ~r/^download-[0-9a-f]{32}\.xml$/
+  end
+
+  test "generates distinct paths without creating files" do
+    paths = for _index <- 1..100, do: TempFile.random_file("feed")
+
+    assert length(Enum.uniq(paths)) == 100
+    refute Enum.any?(paths, &File.exists?/1)
+  end
+end