testID := h.Sum()
	if c.id1 == (cache.ActionID{}) {
		c.id1 = testID
	} else {
		c.id2 = testID
	}
	if cache.DebugTest {
		fmt.Fprintf(os.Stderr, "testcache: %s: test ID %x => %x\n", a.Package.ImportPath, id, testID)
	}

	// Load list of referenced environment variables and files
	// from last run of testID, and compute hash of that content.