Set .__DEVTOOLS__ marker so testthat::with_mocked_bindings() works with loadfast (#12)

* Initial plan

* Set .__DEVTOOLS__ marker so testthat::with_mocked_bindings() works with loadfast

Agent-Logs-Url: https://github.com/finccam/loadfast/sessions/8e755081-78be-4f0d-a46f-bf749eb3bffb

Co-authored-by: ak-finccam <266784444+ak-finccam@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: ak-finccam <266784444+ak-finccam@users.noreply.github.com>

Author: Copilot

R/loadfast.R

@@ -265,6 +265,7 @@ load_fast <- function(path = ".", helpers = TRUE, attach_testthat = NULL, full =
   setNamespaceInfo(ns_env, "dynlibs", NULL)
   setNamespaceInfo(ns_env, "S3methods", matrix(NA_character_, 0L, 4L))
   ns_env[[".__S3MethodsTable__."]] <- new.env(hash = TRUE, parent = baseenv())
+  ns_env[[".__DEVTOOLS__"]] <- new.env(parent = ns_env)
 
   reg <- rlang::ns_registry_env()
   reg[[pkg_name]] <- ns_env

test_loadfast.R

@@ -169,6 +169,33 @@ check("isNamespace() returns TRUE", quote(
   isNamespace(ns)
 ))
 
+check(".__DEVTOOLS__ marker is set (enables testthat mocking)", quote(
+  !is.null(ns[[".__DEVTOOLS__"]])
+))
+
+if (requireNamespace("pkgload", quietly = TRUE)) {
+  check("pkgload::dev_meta() recognizes loadfast-loaded package", quote(
+    !is.null(pkgload::dev_meta("devpackage"))
+  ))
+
+  check("with_mocked_bindings() auto-detects loadfast-loaded package", quote({
+    result <- testthat::with_mocked_bindings(
+      get("add", envir = asNamespace("devpackage"))(1, 2),
+      add = function(a, b) 999L,
+      .package = "devpackage"
+    )
+    result == 999L
+  }))
+
+  check("with_mocked_bindings() without .package uses loadfast-loaded package", quote({
+    result <- testthat::with_mocked_bindings(
+      get("add", envir = asNamespace("devpackage"))(1, 2),
+      add = function(a, b) 999L
+    )
+    result == 999L
+  }))
+}
+
 # --- Search path ---
 check("package:devpackage is on the search path", quote(
   "package:devpackage" %in% search()