tech Guidelines: factories vs new keyword

Author: buskamuza

guides/v2.2/coding-standards/technical-guidelines.md

@@ -49,7 +49,9 @@ Use [RFC2119] to interpret keywords like:
 
 2.1. Object decomposition MUST follow the [SOLID principles].
 
-2.2. Object MUST be ready for use after instantiation. No additional public initialization methods are allowed.
+2.2. Object instantiation
+
+2.2.1. An object MUST be ready for use after instantiation. No additional public initialization methods are allowed.
 
 {% collapsible Examples: %}
 <table>
@@ -98,6 +100,11 @@ class Config
 {% endcollapsible %}
 ---
 
+2.2.2. Factories SHOULD be used for object instantiation instead of `new` keyword. An object SHOULD be replaceable for testing or extensibility purposes.
+Exception: DTOs. There is no behavior in DTOs, so there is no reason for its replaceability.
+Tests can create real DTOs for stubs. 
+Data interfaces,  Exceptions and `Zend_Db_Expr` are examples of DTOs.
+
 {:start="2.3"}
 2.3. Class constructor can have only dependency assignment operations and/or argument validation operations. No other operations are allowed.