![@drpicox
@drpicox
Method that remembers its calls
SPY
32
TESTING TECHNIQUES — TESTING DOUBLES
test("hello world", () => {
const log = []
const outputSpy = message => {
log.push(message)
}
sayHello(outputSpy)
expect(log).toEqual(["hello world"])
})
function sayHello(output) {
output("hello world")
}](https://image.slidesharecdn.com/tdd-05-testingtechniques-210927144638/85/TDD-CrashCourse-Part5-Testing-Techniques-32-320.jpg)
![@drpicox
@drpicox
A spy that validates correctness and knows the object
MOCK
33
TESTING TECHNIQUES — TESTING DOUBLES
class DiskMock {
log = [];
move(cylinder) {
this.log.push('move', cylinder);
}
write(data) {
this.log.push('write', data)
}
isFormatted() {
return this.log.equals('move', 0, 'write', 0)
}
}
test('formats a disk', () => {
const disk = new DiskMock();
format(disk);
expect(disk.isFormatted()).toBeTrue();
})](https://image.slidesharecdn.com/tdd-05-testingtechniques-210927144638/85/TDD-CrashCourse-Part5-Testing-Techniques-33-320.jpg)
TDD CrashCourse Part5: Testing Techniques
- 1. 04 BARCELONA David Ródenas, PhD TDD Course TESTING TECHNIQUES
- 3. @drpicox @drpicox Fast Isolates Repeatable Self-validating Timely F.I.R.S.T. 3 TESTING TECHNIQUES — FIRST
- 4. @drpicox @drpicox Many hundreds or thousands per second Avoid slow logic Data bases External services Intensive computations ... FAST 4 TESTING TECHNIQUES — FIRST
- 5. @drpicox @drpicox Failure reasons become obvious Each test runs individually No assumed initial state Not require other test run f irst Can run alone Can run in random order new , new , new ... ISOLATES 5 TESTING TECHNIQUES — FIRST
- 6. @drpicox @drpicox Run repeatedly in any order, any time No side effects No globals/statics No time No random No databases No services No split test logic ... REPEATABLE 6 TESTING TECHNIQUES — FIRST
- 7. @drpicox @drpicox No manual evaluation required Only two outcomes Red/Green Fail/Pass SELF-VALIDATING 7 TESTING TECHNIQUES — FIRST
- 8. @drpicox @drpicox Written before the code If you write test after code: You do not follow TDD You are not sure that the test works You forget test behaviours Your tests become useless You feel cheeting ... TIMELY 8 TESTING TECHNIQUES — FIRST
- 9. @drpicox @drpicox const notebook = new Notebook() test("add a contact", () => { notebook.add("John", 1234) expect(notebook.get("John")).toBe(1234) }) test("update contact", () => { notebook.update("John", 3456) expect(notebook.get("John")).toBe(3456) }) test("remove a contact", () => { notebook.remove("John") expect(notebook.get("John")).toBeNull() }) EXAMPLE 9 TESTING TECHNIQUES — FIRST
- 10. @drpicox @drpicox test("add a contact", () => { const notebook = new Notebook() notebook.add("John", 1234) expect(notebook.get("John")).toBe(1234) }) test("update contact", () => { const notebook = new Notebook() notebook.add("John", 1234) notebook.update("John", 3456) expect(notebook.get("John")).toBe(3456) }) test("remove a contact", () => { const notebook = new Notebook() notebook.add("John", 1234) notebook.remove("John") expect(notebook.get("John")).toBeNull() }) EXAMPLE 10 TESTING TECHNIQUES — FIRST
- 11. @drpicox @drpicox // Date changes each time new Date(); // Result changes each call Random.next(); // We are accessing a static/global Notebook.add("John", 1234); // Global + It is not self-validated if (notebook.get("John") === 1234) System.out.println("Sucess") EXAMPLE 11 TESTING TECHNIQUES — FIRST
- 13. @drpicox @drpicox Arrange Prepare the initial states Call news and required sets before act Act Execute the actions required by the test Assert Gather results Expect the result values AAA STRUCTURE 13 TESTING TECHNIQUES — AAA
- 14. @drpicox @drpicox Order is always kept Steps are not mixed Expect always simple results AAA STRUCTURE 14 TESTING TECHNIQUES — AAA
- 15. @drpicox @drpicox test("manage contacts", () => { const notebook = new Notebook() // Arrange notebook.add("John", 1234) // Act expect(notebook.get("John")).toBe(1234) // Assert notebook.update("John", 3456) // Act expect(notebook.get("John")).toBe(3456) // Assert notebook.delete("John") // Act expect(notebook.get("John")).toBeNull() // Assert }) EXAMPLE 15 TESTING TECHNIQUES — AAA
- 16. @drpicox @drpicox test("add contact", () => { // Arrange const notebook = new Notebook() // Act notebook.add("John", 1234) // Assert expect(notebook.get("John")).toBe(1234) }) test("update contact", () => { // Arrange const notebook = new Notebook() notebook.add("John", 1234) // Act notebook.update("John", 3456) // Assert expect(notebook.get("John")).toBe(3456) }) ... EXAMPLE 16 TESTING TECHNIQUES — AAA
- 17. @drpicox @drpicox Dispose/clean resources as fourth A ANNIHILATE 17 TESTING TECHNIQUES — AAA AAAA
- 19. @drpicox @drpicox CODE COVERAGE 19 TESTING TECHNIQUES — CODE COVERAGE Code Tested Code Existing %
- 20. @drpicox @drpicox test("add contact", () => { const notebook = new Notebook() notebook.add("John", 1234) expect(notebook.get("John")).toBe(1234) }) class Notebook { add(name, phone) { if (map.contains(name)) throw new Error(`Cannot add twice ${name}`) map.put(name, phone) } } EXAMPLE 20 TESTING TECHNIQUES — CODE COVERAGE Code Coverage: 66% Uncovered line
- 21. @drpicox @drpicox test("add contact", () => { const notebook = new Notebook() notebook.add("John", 1234) expect(notebook.get("John")).toBe(1234) }) test('cannot add a duplicated contact', () => { const notebook = new Notebook() notebook.add("John", 1234) expect(() => notebook.add('John', 1111)).toThrow() }) class Notebook { add(name, phone) { if (map.contains(name)) throw new Error(`Cannot add twice ${name}`) map.put(name, phone) } } FIX: ADD TEST 21 TESTING TECHNIQUES — CODE COVERAGE Code Coverage: 100%
- 22. @drpicox @drpicox test("add contact", () => { const notebook = new Notebook() notebook.add("John", 1234) expect(notebook.get("John")).toBe(1234) }) class Notebook { add(name, phone) { map.put(name, phone) } } FIX: REMOVE CODE 22 TESTING TECHNIQUES — CODE COVERAGE Code Coverage: 100%
- 23. @drpicox @drpicox WHICH FIX IS BETTER? 23 TESTING TECHNIQUES — CODE COVERAGE IT DEPENDS! Add a Test Case Remove uncovered code? Test Fast replaces (Java) Fail Fast Does the case make sense? Is there a business case related? Can it happen? It worth the code to maintain? First to check Do not modify business cases Do not add replicated checks
- 24. @drpicox @drpicox 1 test base 1 test per condition &&, ||, if, while, for, ... 1 test per switch cases + 1 for default Default is always present, even if it is not written NUMBER OF TESTS 24 TESTING TECHNIQUES — CODE COVERAGE
- 25. @drpicox @drpicox Main Dates Randoms Network ... CANNOT COVER 25 TESTING TECHNIQUES — CODE COVERAGE
- 26. @drpicox @drpicox LIMITS 26 TESTING TECHNIQUES — CODE COVERAGE “Every well designed system has at least one dirty component, usually associated with main. Nothing outside this component depends on anything inside it. All dependencies point outward. This is where you put switches, factories, and IOC.” https://twitter.com/unclebobmartin/status/1122138039390806016
- 27. @drpicox @drpicox 100% Code Coverage DO NOT ensure correctness With TDD Code Coverage should be 100% It is a hint it reveals what went wrong what we missed which cases we implemented but not planned shows which code remove QUALITY 27 TESTING TECHNIQUES — CODE COVERAGE
- 29. @drpicox @drpicox Replaces data/object with one created by the test 5 types Dummy Stub Spy Mock Fake TEST DOUBLES 29 TESTING TECHNIQUES — TESTING DOUBLES
- 30. @drpicox @drpicox Null, 0 or a plain value that can replace an argument DUMMY 30 TESTING TECHNIQUES — TESTING DOUBLES test("count created accounts", () => { const bank = new Bank() bank.createAccount("John", null) expect(bank.count()).toBe(1) }) class Bank { createAccount(name, fiscalData) { accounts.put(name, fiscalData) } }
- 31. @drpicox @drpicox A value need for the test that the code uses STUB 31 TESTING TECHNIQUES — TESTING DOUBLES test("gives heads", () => { const random = { next() { return 0 }, } const result = flipCoin(random) expect(result).toBe("head") }) function flipCoin(random) { if (random.next() < 0.5) return "head" return "tails" }
- 32. @drpicox @drpicox Method that remembers its calls SPY 32 TESTING TECHNIQUES — TESTING DOUBLES test("hello world", () => { const log = [] const outputSpy = message => { log.push(message) } sayHello(outputSpy) expect(log).toEqual(["hello world"]) }) function sayHello(output) { output("hello world") }
- 33. @drpicox @drpicox A spy that validates correctness and knows the object MOCK 33 TESTING TECHNIQUES — TESTING DOUBLES class DiskMock { log = []; move(cylinder) { this.log.push('move', cylinder); } write(data) { this.log.push('write', data) } isFormatted() { return this.log.equals('move', 0, 'write', 0) } } test('formats a disk', () => { const disk = new DiskMock(); format(disk); expect(disk.isFormatted()).toBeTrue(); })
- 34. @drpicox @drpicox An functional object that replaces an original one FAKE 34 TESTING TECHNIQUES — TESTING DOUBLES test("deposit cash", () => { const db = new InMemoryDB() const bank = new Bank(db) bank.createAccount("John") bank.deposit("John", 100) expect(bank.get("John")).toBe(100) })
- 35. @drpicox @drpicox Test Doubles may Reduce Coverage Although, some cases are necessary Test Doubles Reduce Con f idence CONFIDENCE 35 TESTING TECHNIQUES — TESTING DOUBLES