Notes

Question 1

Boy Scout Rule

Answer 1

Check-in our code a little cleaner than when we checked it out

Question 2

Rules for Meaningful Names

Answer 2

1) Pronounceable
2) Searchable
3) Class Names are noun or noun phrases
4) Methods are verb or verb phrases
5) Do not pun - same word for two purposes

Question 3

Rules for Functions

Answer 3

1) They should be small
2) Do One Thing. Note, passing flag argument proclaims a function does more than one thing. Do not do this.
3) Max two or three arguments. If more, it is likely that some of those arguments ought to be wrapped into a class of their own.
4) Command Query Separation
5) Extract Try/Catch Blocks

Question 4

What is Command Query Separation

Answer 4

Functions should either do something or answer something, but not both

Question 5

What is a guideline for error handling in a function?

Answer 5

If the keyword try exists in a function, it should be the very first word in the function and there should be nothing after the catch/finally blocks.

Question 6

What are Good Comments?

Answer 6

1) Legal Comments
2) Informative Comments such as explaining a regex pattern.
3) Explanation of Intent
4) Clarification
5) Warning of Consequence (ex: really long test case)
6) Amplification - amplify line otherwise might be inconsequential.

Question 7

Name three formatting goals

Answer 7

neatness, consistency, and attention to detail

Question 8

Describe dependent function formatting

Answer 8

If one function calls another, they should be vertically close, and the caller should be above the callee, if at all possible. This gives the program natural flow.

Question 9

What is the Law of Demeter?

Answer 9

Objects hide their data and expose operations. More precisely, a method f of a class C should only call the methods of these:

1) C
2) An object created by f
3) An object passed as an argument to f
4) An object held in an instance variable of C

Question 10

What is a DTO?

Answer 10

Data Transfer Object. Class with public variables and no functions.

Question 11

What is an Active Record?

Answer 11

A special form of DTO. They are data structures with public variables; but they typically have navigational methods like save and find.

Question 12

Why wrap third party APIs?

Answer 12

When you wrap a third-party API, you minimize your dependencies upon it. You can choose to move to a different library in the future without much penalty.

Question 13

What are learning tests?

Answer 13

Writing tests to explore our understanding of third-party code. We call a third-party API, as we expect to use in our application.

Question 14

The Three Laws of TDD

Answer 14

1) You may not write production code until you have written a failing unit test.
2) You may not write more of a unit test than is sufficient to fail, and not compiling is failing.
3) You may not write more production code than is sufficient to pass the currently failing test.

Question 15

What’s the most important aspect of a clean test?

Answer 15

Readability. Specifically clarity, simplicity and density of expression. In a test you want to say a lot with a few expressions as possible.

Question 16

What is the Build-Operate-Check pattern?

Answer 16

Each test is clearly split into three parts. The first part builds up the test data, the second part operates on that test data, and the third part checks that the operation yielded the expected results.

Question 17

What is a good rule for asserts in your tests?

Answer 17

The number of asserts in a test ought to be minimized. We want to test a single concept in each test function.

Question 18

Define F.I.R.S.T. clean tests

Answer 18

Fast: Test should run quickly.
Independent: Tests shouldn’t depend on each other. One test shouldn’t set up the conditions for the next.
Repeatable: Run in any environment.
Self-Validating: Should have boolean output.
Timely: Unit tests should be written just before the production code that makes them pass.

Question 19

What is the first rule of a class?

Answer 19

Classes should be small. We use a responsibility measurement for length.

Question 20

What’s the single responsibility principle?

Answer 20

It states, that a class or module should have one and only one reason to change.

Question 21

What is Cohesion?

Answer 21

Classes should have a small number of instance variables. Each of the methods of a class should manipulate one or more of those variables. In general, the more variables a method manipulates the more cohesive that method is to its class.

Question 22

What should we be able to do when describing a class?

Answer 22

Describe it in about 25 words or less, without using the words “if”, “and”, “or”, or “but”

Question 23

What is the essence of iterative and incremental agility?

Answer 23

It is a myth that we can get systems “right the first time.” Instead, we should implement only today’s stories, then refractor and expand the system to implement new stories tomorrow.

Question 24

Describe starting “naively simple”

Answer 24

We can start a software project with a “naively simple” but nicely decoupled architecture, delivering working user stories quickly, and then adding more infrastructure as we scale up.

Question 25

Feature Envy

Answer 25

The methods of a class should be interested in the variables and functions of the class they belong to, and not the variables and functions of other classes. When a method uses accessors and mutators of some other object to manipulate the data within that object, then it envies the scope of the class of that other object. It wishes it were inside that other class so that it could have direct access to the variables it is manipulating.

Question 26

Selector Arguments

Answer 26

Type of argument that is used to select the behavior of the function.

Question 27

Describe use of explanatory variables

Answer 27

One of the more powerful ways to make a program readable is to break the calculations up into intermediate values that are held in variables with meaningful names.