Why testing ensures app quality in iOS Swift - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a simple unit test method in Swift.

iOS Swift

func testExample() {
    let result = 2 + 2
    XCTAssertEqual(result, [1])
}

Drag options to blanks, or click blank then click option'

A3

B5

C4

D22

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong expected value like 3 or 5.

Confusing the actual result with the expected value.

The test checks if 2 + 2 equals 4, so the expected value is 4.

2fill in blank

medium

Complete the code to launch the app and check if a button exists in UI testing.

iOS Swift

let app = XCUIApplication()
app.launch()
let button = app.buttons["Submit"]
XCTAssertTrue(button.[1])

Drag options to blanks, or click blank then click option'

AisHidden

Bexists

CisEnabled

DisSelected

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'isHidden' which checks visibility, not presence.

Using 'isEnabled' which checks if the button can be tapped.

To verify the button is present, we check if it exists.

3fill in blank

hard

Fix the error in the test assertion to correctly check if a label's text equals "Hello".

iOS Swift

let label = app.staticTexts["greetingLabel"]
XCTAssertEqual(label.[1], "Hello")

Drag options to blanks, or click blank then click option'

Avalue

BlabelText

Clabel

Dtext

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'text' which is not a valid property in XCUIElement.

Using 'label' which is a property but not the text content.

In UI tests, the label's text is accessed via the 'value' property.

4fill in blank

hard

Fill both blanks to create a test that waits for a button to appear before tapping it.

iOS Swift

let app = XCUIApplication()
let button = app.buttons["Continue"]
let exists = NSPredicate(format: "[1] == true")
expectation(for: exists, evaluatedWith: button, handler: nil)
waitForExpectations(timeout: [2], handler: nil)
button.tap()

Drag options to blanks, or click blank then click option'

Aexists

BisEnabled

C5

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'isEnabled' instead of 'exists' in the predicate.

Setting the timeout too low or too high.

We wait for the button's 'exists' property to be true, with a timeout of 10 seconds.

5fill in blank

hard

Fill all three blanks to write a unit test that checks if a function returns true for valid input.

iOS Swift

func testIsValid() {
    let input = "[e-mail]"
    let result = Validator.[1](input: input)
    XCTAssert[2](result)
    XCTAssertFalse(Validator.[3](input: ""))
}

Drag options to blanks, or click blank then click option'

AisValidEmail

BTrue

DFalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using XCTAssertFalse for the valid input check.

Mixing up function names.

The test calls 'isValidEmail' to check the input, asserts true for valid input, and false for empty input.

Practice

1. Why is testing important for mobile apps?
Testing helps to:

easy

A. Make the app run faster on all devices

B. Reduce the app size on the device

C. Add new features automatically

D. Find bugs before users encounter them

Solution

1. Step 1: Understand the purpose of testing

   Testing is done to catch errors or bugs early, before users find them.

2. Step 2: Compare options with testing goals

   Only Find bugs before users encounter them matches the main goal of testing, which is bug detection.

3. Final Answer:

   Find bugs before users encounter them -> Option D

4. Quick Check:

   Testing finds bugs early = B [OK]

Hint: Testing finds bugs early to improve app quality [OK]

Common Mistakes:

• Confusing testing with performance optimization
• Thinking testing adds features automatically
• Believing testing reduces app size

2. Which Swift code snippet correctly defines a simple test function?

easy

A. func testExample() { XCTAssertTrue(true) }

B. func testExample { XCTAssertTrue(true) }

C. func testExample() -> Bool { return true }

D. testExample() { XCTAssertTrue(true) }

Solution

1. Step 1: Check Swift function syntax

   Functions need parentheses () after the name and braces {} around the body.

2. Step 2: Identify correct test function format

   func testExample() { XCTAssertTrue(true) } correctly defines a function with parentheses and calls XCTAssertTrue inside.

3. Final Answer:

   func testExample() { XCTAssertTrue(true) } -> Option A

4. Quick Check:

   Correct Swift function syntax = A [OK]

Hint: Swift functions need () after name and {} for body [OK]

Common Mistakes:

• Omitting parentheses after function name
• Missing braces around function body
• Returning a value in a test function

3. What will be the output when this test runs?

func testSum() {
  let result = 2 + 3
  XCTAssertEqual(result, 5)
}

medium

A. Syntax error in test function

B. Test fails with error

C. Test passes with no errors

D. Test is skipped automatically

Solution

1. Step 1: Evaluate the calculation in testSum()

   The sum 2 + 3 equals 5, so result is 5.

2. Step 2: Check XCTAssertEqual condition

   XCTAssertEqual compares result (5) with expected value (5), which matches.

3. Final Answer:

   Test passes with no errors -> Option C

4. Quick Check:

   Correct assertion means test passes = A [OK]

Hint: If values match XCTAssertEqual, test passes [OK]

Common Mistakes:

• Assuming test fails if no print output
• Confusing XCTAssertEqual with XCTAssertTrue
• Thinking test runs only if called explicitly

4. Identify the error in this test code:

func testIsEven() {
  let number = 4
  XCTAssertTrue(number % 2 == 1)
}

medium

A. Syntax error in XCTAssertTrue usage

B. The test incorrectly checks for odd instead of even

C. Missing return type in function

D. Variable number should be a constant

Solution

1. Step 1: Understand the test purpose

   The function name suggests checking if number is even.

2. Step 2: Analyze the assertion condition

   number % 2 == 1 checks if number is odd, which is wrong for even check.

3. Final Answer:

   The test incorrectly checks for odd instead of even -> Option B

4. Quick Check:

   Mismatch between test name and condition = C [OK]

Hint: Check if test condition matches test name intent [OK]

Common Mistakes:

• Confusing odd and even conditions
• Ignoring test function naming conventions
• Assuming syntax error when logic is wrong

5. How does automated testing help maintain app quality after adding new features?

hard

A. By running tests to catch bugs introduced by changes

B. By automatically rewriting code for better performance

C. By reducing the app size after new features

D. By disabling old features to avoid conflicts

Solution

1. Step 1: Understand automated testing role

   Automated tests run existing checks quickly after code changes.

2. Step 2: Identify how tests maintain quality

   They catch bugs early that new features might cause, preventing issues.

3. Final Answer:

   By running tests to catch bugs introduced by changes -> Option A

4. Quick Check:

   Automated tests catch new bugs = D [OK]

Hint: Tests catch bugs after changes to keep app stable [OK]

Common Mistakes:

• Thinking tests rewrite or optimize code
• Believing tests reduce app size
• Assuming tests disable old features