Document single DynamicNode as return value

Addresses #1521

documentation/src/docs/asciidoc/user-guide/writing-tests.adoc

@@ -1278,12 +1278,13 @@ generated at runtime by a factory method that is annotated with `@TestFactory`.
 
 In contrast to `@Test` methods, a `@TestFactory` method is not itself a test case but
 rather a factory for test cases. Thus, a dynamic test is the product of a factory.
-Technically speaking, a `@TestFactory` method must return a `Stream`, `Collection`,
-`Iterable`, `Iterator`, or array of `DynamicNode` instances. Instantiable subclasses of
-`DynamicNode` are `DynamicContainer` and `DynamicTest`. `DynamicContainer` instances are
-composed of a _display name_ and a list of dynamic child nodes, enabling the creation of
-arbitrarily nested hierarchies of dynamic nodes. `DynamicTest` instances will be
-executed lazily, enabling dynamic and even non-deterministic generation of test cases.
+Technically speaking, a `@TestFactory` method must return a single `DynamicNode` or a
+`Stream`, `Collection`, `Iterable`, `Iterator`, or array of `DynamicNode` instances.
+Instantiable subclasses of `DynamicNode` are `DynamicContainer` and `DynamicTest`.
+`DynamicContainer` instances are composed of a _display name_ and a list of dynamic child
+nodes, enabling the creation of arbitrarily nested hierarchies of dynamic nodes.
+`DynamicTest` instances will be executed lazily, enabling dynamic and even non-deterministic
+generation of test cases.
 
 Any `Stream` returned by a `@TestFactory` will be properly closed by calling
 `stream.close()`, making it safe to use a resource such as `Files.lines()`.