Update testing.md
Fixed Parameter Generator table
diff --git a/docs/reference/testing.md b/docs/reference/testing.md
index 62cdcc1..877dfa3 100644
--- a/docs/reference/testing.md
+++ b/docs/reference/testing.md
@@ -110,6 +110,7 @@
| `Bool()` | Yields sequence `{false, true}`. |
| `Combine(g1, g2, ..., gN)` | Yields as `std::tuple` *n*-tuples all combinations (Cartesian product) of the values generated by the given *n* generators `g1`, `g2`, ..., `gN`. |
| `ConvertGenerator<T>(g)` | Yields values generated by generator `g`, `static_cast` to `T`. |
+
The optional last argument *`name_generator`* is a function or functor that
generates custom test name suffixes based on the test parameters. The function
must accept an argument of type
