Writing testable code

I write unit tests so the code works as expected. There are guidelines for writing testable code.

Here are some flaws when designing code that makes it difficult for tests:

• Constructor does work.
  1. It violates the single responsiblity principle
  2. Testing is directly difficult
  3. Subclassing and overriding to test is flawed
  4. Forces collaborators on you
• Digging into Collaborators(Law of Demeter).
  1. Deceitful API
  2. Makes for brittle code
  3. Bloats code and complicates what is really happening
  4. Hard for testing
• Global state and singletons.
  1. Global state dirties design
  2. Global state enables spooky action at a distance
  3. Global state and singletons makes brittle application and tests
  4. Global state and singletons makes APIs into liars
  5. Globality and Global load is transitive
  6. A singleton is Global state
  7. Global state in Tests is an really bad
• Class does too much.
  1. Hard to debug
  2. Hard to test
  3. Non-extensible
  4. Not subject to altering behavior via standard mechanisms: decorator, strategy
  5. Difficult to give a name to what the class does.