for len(tmpdir) < 400 {
		tmpdir += "/dir3456789"
	}
	for _, sz := range sizes {
		t.Run(fmt.Sprintf("length=%d", sz), func(t *testing.T) {
			sizedTempDir := tmpdir[:sz-1] + "x" // Ensure it does not end with a slash.

			// The various sized runs are for this call to trigger the boundary
			// condition.
			if err := MkdirAll(sizedTempDir, 0755); err != nil {
				t.Fatalf("MkdirAll failed: %v", err)
			}