Writing Conditionals and Practicing TDD TDD Refresher RED

TDD Refresher • RED – write the test and watch it fail – Why

Chapter Project • This chapter’s project is a tax calculator • You will write

If Statements • Used when we want something to happen only under certain conditions

if-then-else Statements • Used when we want to choose between two different behaviors then

Why have the curly brackets? • Exactly one statement after the condition is considered

Watch the semi-colon • What will this code do? if (potato. Number != 4);

Testing Conditionals • Clearly, we cannot test every value that a system might see,

Nested Conditionals What is the output for 95? 85? 75? 90? 80? What are

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Writing Conditionals and Practicing TDD

TDD Refresher • RED – write the test and watch it fail – Why do we watch it fail? • GREEN – write the simplest code that can make it pass • REFACTOR – cleanup – comments – variable names – eliminate duplication (pay attention to duplication between the values the test knows and the values the code knows)

Chapter Project • This chapter’s project is a tax calculator • You will write a series of methods that make a series of tests pass. • The goal is to practice writing conditional statements

If Statements • Used when we want something to happen only under certain conditions then block if (potato. Number != 4) { System. out. print(" potato"); } condition

if-then-else Statements • Used when we want to choose between two different behaviors then block else block long result = one. Back + two. Back; if (result < one. Back) { one. Back = 1; two. Back = 0; result = 1; } else { two. Back = one. Back; one. Back = result; } condition

Why have the curly brackets? • Exactly one statement after the condition is considered to be inside the condition • Those brackets make one statement out of a sequence of statements if (potato. Number != 4) { System. out. print(" potato"); halfway = true; }

Watch the semi-colon • What will this code do? if (potato. Number != 4); { System. out. print(" potato"); } notice the semi-colon That semi-colon ends the one statement in then block, so the rest of the code is NOT part of the if statement (and will always be executed).

Testing Conditionals • Clearly, we cannot test every value that a system might see, so we need to target our tests on values that are likely to cause errors. • Border case - A situation where a small change in input causes a fundamentally different behavior. • Focus the tests on the values around that situation because those are the values where we are most likely to have a defect

Nested Conditionals What is the output for 95? 85? 75? 90? 80? What are the border cases? if (grade > 90) { System. out. println("Excellent"); } else { if (grade > 80) { System. out. println("Average"); } else { System. out. println("Poor"); } }