feat(agent): add Diagnostics module with no-op default

agent/test/proxmox_agent/diagnostics_test.exs

@@ -0,0 +1,64 @@
+defmodule ProxmoxAgent.DiagnosticsTest do
+  use ExUnit.Case, async: false
+
+  alias ProxmoxAgent.Diagnostics
+
+  setup do
+    # Isolate tests: clear the env key before and after each test.
+    Application.delete_env(:agent, :dump_dir)
+    on_exit(fn -> Application.delete_env(:agent, :dump_dir) end)
+    :ok
+  end
+
+  describe "configure/1 and enabled?/0" do
+    test "nil disables and returns :ok" do
+      assert :ok = Diagnostics.configure(nil)
+      refute Diagnostics.enabled?()
+    end
+
+    test "empty string disables and returns :ok" do
+      assert :ok = Diagnostics.configure("")
+      refute Diagnostics.enabled?()
+    end
+
+    test "valid path creates the directory and enables" do
+      dir = Path.join(System.tmp_dir!(), "diag-#{System.unique_integer([:positive])}")
+      on_exit(fn -> File.rm_rf(dir) end)
+
+      assert :ok = Diagnostics.configure(dir)
+      assert Diagnostics.enabled?()
+      assert File.dir?(dir)
+      assert Application.get_env(:agent, :dump_dir) == dir
+    end
+
+    test "unreachable path disables (does not crash)" do
+      # Point at a path under a non-directory file to force mkdir_p failure.
+      parent = Path.join(System.tmp_dir!(), "diag-parent-#{System.unique_integer([:positive])}")
+      File.write!(parent, "not a directory")
+      dir = Path.join(parent, "child")
+      on_exit(fn -> File.rm_rf(parent) end)
+
+      assert :ok = Diagnostics.configure(dir)
+      refute Diagnostics.enabled?()
+    end
+  end
+
+  describe "log_command/4 and log_sample/2 (no writer running)" do
+    test "log_command/4 no-ops and returns :ok when disabled" do
+      assert :ok = Diagnostics.log_command("zpool", ["list"], {:ok, "body"}, 1_234)
+    end
+
+    test "log_sample/2 no-ops and returns :ok when disabled" do
+      assert :ok = Diagnostics.log_sample("fast", %{foo: "bar"})
+    end
+
+    test "log_command/4 no-ops when enabled but writer is not running" do
+      dir = Path.join(System.tmp_dir!(), "diag-#{System.unique_integer([:positive])}")
+      on_exit(fn -> File.rm_rf(dir) end)
+
+      :ok = Diagnostics.configure(dir)
+      # Writer is not started in this test — log should still be safe.
+      assert :ok = Diagnostics.log_command("zpool", ["list"], {:ok, "body"}, 1_234)
+    end
+  end
+end