mi: limit the CIM_DataFile cancellation test to one directory (#2752)

Signed-off-by: Jan-Otto Kröpke <mail@jkroepke.de>

internal/mi/AGENTS.md

@@ -63,5 +63,12 @@ results never look complete. A context that is done after the final result
 (`complete`, set under `mu`) does not fail a query that has nothing left to
 hand over.
 
+Tests that need a slow query must bound the work it causes. Cancelling an
+operation may end it only on the client: providers such as CIMWin32
+(`CIM_DataFile`) keep enumerating in WmiPrvSE. `CIM_DataFile` for a whole drive
+kept the CI runner busy for minutes after the Go tests, which slowed every
+later step and made the end-to-end `/metrics` request time out. Restrict such
+queries to one directory.
+
 Run `CGO_ENABLED=1 go test -race` (gcc from w64devkit) and a
 `-gcflags=all=-d=checkptr` run for changes in this package.

internal/mi/callbacks_test.go

@@ -327,9 +327,11 @@ func Test_MI_QueryContext_CancelDuringQuery(t *testing.T) {
 	})
 
 	t.Run("QueryContext", func(t *testing.T) {
-		// CIM_DataFile enumerates every file of the drive, which takes far
-		// longer than the context.
-		slowQuery, err := mi.NewQuery("SELECT Name FROM CIM_DataFile WHERE Drive = 'C:'")
+		// CIM_DataFile is slow, so the query outlives the context. Cancel
+		// does not stop the CIMWin32 provider in WmiPrvSE: it finishes the
+		// enumeration on its own. Keep the query to one directory; a whole
+		// drive keeps the runner busy for minutes after the test.
+		slowQuery, err := mi.NewQuery(`SELECT Name FROM CIM_DataFile WHERE Drive = 'C:' AND Path = '\\Windows\\System32\\'`)
 		require.NoError(t, err)
 
 		ctx, cancel := context.WithTimeout(t.Context(), 100*time.Millisecond)