UncleBobVideoStore

The video store example from Episode 3 of cleancoders.com. Based upon, but not identical to, the first chapter of Martin Fowler's classic book: Refactoring.

JAD

I made some changes from the original

• Made a Maven project
• Migrated the original text written in Junit 3 to Junit5

Step 1

Observe

• Very old code like written by C++ programmer
• Variables in some classes are placed at bottom
• Test class has long lines which make us scroll horizontally right
• Yuck
• Tests pass

Activity

• Break the strings in the test methods into multiple parts
• Makes methods visible all in one screen
• No scrolling to right needed

Step 2

Observe

• All test methods are testing UI that is actual report
• All they need to test is the amounts calculated
• UI string test can be there in one of the tests for completeness
• Repetition of UI strings introduce regression impact

Activity

• Move all variables in all classes to top
• Add assertions with code as below

assertEquals(9.0, customer.getTotalAmount(), DELTA);
assertEquals(2, customer.getFrequentRenterPoints());

• Create the necessary methods required with IDE intellisense
• Promote variables totalAmount and frequentRenterPoints to fields, keep init in current method
• Remove the string comparison in first test
• Just execute customer.statement(); to generate them

Step 3

Observe

• Customer class is just generating a statement
• It has nothing to do with a customer other than maintaining a variable of Customer customerName

Activity

• Rename Customer class to Statement
• Rename name in Statement class to customerName
• Rename statement method to generate
• Change all test methods to assert calculated values
• Duplicate last test to maintain one of them as testing string
• Add suffix format to the last method
• Add suffix Totals to all other test methods
• Keep the string comparison as is in last method

Step 4

Activity

• Change Fred to Customer in customer name
• Change the format method to reflect this change
• extract field for new Movie("The Cell", Movie.NEW_RELEASE) with name newReleaseMovie1
• extract new Movie("The Tigger Movie", Movie.NEW_RELEASE) into field newReleaseMovie2
• change title of The Cell to New Release 1
• change title of The Tiger Movie to New Release 2
• change all movies to variables and titles to generic titles
• change the format method to reflect the changes

Step 5

Activity

• generate method of the Statement class
• extract the statements which initialize to method named initialize()

totalAmount = 0;
frequentRenterPoints = 0;

• Rename result variable to statementText
• extract method for createHeader()
• Change return value of createHeader() to MessageFormat.format()

Step 6

Observe

• while loop in the generate method just adds rental lines to the statement

Activity

• Extract while loop in method named createRentalLines()
• Remove the params and eliminate side effects
• Rename statementText to rentalLinesText in createRentalLines() method
• Combine footer test strings and format to multiple lines
• Extract footer logic to createFooter()
• Rename initialize() method to clearTotals()
• Change return value in createFooter() to MessageFormat.format()
• Change the order of methods in order of calls
• Step down method of ordering methods
• Remove unused getCustomerName() method
• Extract body of while loop from method createRentalLines() to method named createRentalLine()
• Rename variable rentalLinesText to rentalLineText in method createRentalLine()
• Rename parameter each to rental in method createRentalLine()

Step 7

Activity

• Extract the switch statement into method named determineAmount() using comment content for name
• Do not pass thisAmount variable
• Rename variable thisAmount to rentalAmount in method determineAmount and createRentalLine
• Extract frequentRenterPoints login into method determineFrequentRenterPoints
• Modify method to make it simpler and return value without side effect

Step 8

Activity

• Extract condition in determineFrequentRenterPoints method into a variable
• Name it bonusIsEarned
• Rearrange all calculations at top in createRentalLine
• Extract formatting of rental lines into method formatRentalLines
• Remove variable declaration
• Change return value to MessageFormat.format() call
• Inline variable for createRentalLine() method return value
• Remove demeter law violation for rental.getMovie().getTitle()
• In method formatRentalLines
• Making method call like rental.getTitle()
• Rearrange methods of Statement class for step down method

Step 9

Observe

• determineAmount() method is not cohesive
• It does not use any fields in statement class
• It does not belong to Statement class
• In fact, it should belong to Rental class as it uses methods from that class
• same true with method determineFrequentRenterPoints

Activity

• Move the method determineAmount() to Rental class as public
• change calls to getMovie() and getDaysRented() to field variables
• Move determineFrequentRenterPoints method to Rental class
• change calls to getMovie() and getDaysRented() to field variables

Step 10

Observe

• In Rental class determineAmount(), we use four things from movie and only one thing from Rental
• This method hence belongs to Movie class
• Same with method determineFrequentRenterPoints()

Activity

• Add signatures of method like follows

public double determineAmount() {
    return determineAmount(daysRented);
}
public double determineAmount(int daysRented) {
...
}

• Move the method with argument to Movie class
• Fix the rental this issue
• Same Move with determineFrequentRenterPoints() method to Movie
• Inline priceCode in both methods

Step 11

Observe

• determineAmount() in Movie is using switch
• it should use polymorphic dispatch
• we have to do this without breaking code

Activity

• In Test class
• Change the Movie class names to subclasses to create them with IDE
• remove the second parameter from constructors as it is redundant now
• In Movie class for determineAmount() method
• use refactoring Push Members Down, keep in Movie as abstract
• Run with coverage and remove unused code from all subclasses
• Remove the type codes of Movies now as they are redundant
• Change signature of constructor of Movie and remove priceCode

Step 12 - JAD Bonus

Activity

• Go to settings > Editor > Code inspection > Code style issues
• check instance field access not qualified with this
• check instance method access not qualified with this
• Run code analysis on videostore package
• Fix all issues